Biospeciation and antidiabetic effects of oxidovanadium(IV) complexes
- Authors: Ugirinema, Vital
- Date: 2014
- Subjects: Vanadium compounds , Diabetes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10442 , http://hdl.handle.net/10948/d1020973
- Description: The syntheses of bis(1R-imidazole-2/4-carboxylato)oxidovanadium(IV) complexes was successfully carried out and the complexes were isolated in the solid state. The coordinated water was confirmed by elemental analyses, and single crystal XRD. The complexes were therefore distorted octahedral rather than square planar due to the coordination of water at the sixth position. The reaction of the vanadyl ion (VO2+) with imidazole-4-carboxylic acid (Im4COOH), imidazole-2-carboxylic acid (Im2COOH) and methylimidazole-2-carboxylic acid (MeIm2COOH), respectively, in the presence of small bioligands (bL) [oxalate (Ox), lactate (Lact), and phosphate (Phos)] and high molecular weight (HMM) human serum proteins [albumin (HSA) and transferrin (hTf)] were studied in aqueous solution using potentiometric acid base titrations under oxygen and carbon dioxide–free conditions. The data obtained from these titrations was used to calculate the binary and ternary stability constants using the programme HYPERQUAD. The overall stability constants for VO2+-L-Ox system (log β1111 = 18.9, 18.79 and 19.86), VO2+-L-Lact system (log β1111 = 21.83, 20.98 and 22.86), and VO2+-L-Phos system (log β1111 = 27.35, 24.16 and 27.42) (for L= Im4COOH, Im2COOH and MeIm2COOH, respectively) were obtained. The species distribution diagrams showed that under physiological pH the following ternary and quaternary species; [(VO)L(bL)], and [VO(L)(bL)(OH)], would dominate provided that the competition with serum proteins is not too strong. These species were also confirmed by HPLC, LC-MS and EPR. The overall stability constants for the VO2+-L-HSA system (log β2,1,1,0 = 24.3, 23.7 and 24.7), and for the VO2+-L-hTf system (log β2,2,1,0 = 31.1, 30.8, 36.4 for L = Im4COOH, Im2COOH and MeIm2COOH, respectively), suggesting stronger binding of transferrin. The formation constants for the formation of binary (VO(IV) and the proteins) were 9.1 and 13 for log β11, and 20.9 and 25.2 for β12, for human serum albumin and human serum transferrin respectively. The species distribution diagrams for the proteins (HMM) with oxidovanadium(IV) under physiological pH was dominated by VO(HMM)2, VOL(HMM) for unsubstituted Im4COOH and Im2COOH, however, for the N-substituted MeIm2COOH, the species distribution diagrams under physiological pH, were dominated by VOL2, VO(HMM)2 and VO2L2(HMM). These species were further confirmed by HPLC, MALDI-TOF-MS and EPR. The glucose stimulated insulin secretion (GSIS) action of the complexes was investigated using INS-1E cells at 1μM concentration which was established through cytotoxicity studies via the MTT assay. The vanadium salt (VOSO4), cationic vanadium(IV) complex ([VO(MeImCH2OH)2]2+) were also included in the GSIS study in addition to the three neutral complexes [VO(Im4COO)2, VO(Im2COO)2 and VO(MeIm2COO)2] for comparison. The neutral complexes, especially VO(MeIm2COO)2, showed promising results in the stimulation of insulin secretion than the cationic complex and the vanadium salt.
- Full Text:
- Date Issued: 2014
- Authors: Ugirinema, Vital
- Date: 2014
- Subjects: Vanadium compounds , Diabetes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10442 , http://hdl.handle.net/10948/d1020973
- Description: The syntheses of bis(1R-imidazole-2/4-carboxylato)oxidovanadium(IV) complexes was successfully carried out and the complexes were isolated in the solid state. The coordinated water was confirmed by elemental analyses, and single crystal XRD. The complexes were therefore distorted octahedral rather than square planar due to the coordination of water at the sixth position. The reaction of the vanadyl ion (VO2+) with imidazole-4-carboxylic acid (Im4COOH), imidazole-2-carboxylic acid (Im2COOH) and methylimidazole-2-carboxylic acid (MeIm2COOH), respectively, in the presence of small bioligands (bL) [oxalate (Ox), lactate (Lact), and phosphate (Phos)] and high molecular weight (HMM) human serum proteins [albumin (HSA) and transferrin (hTf)] were studied in aqueous solution using potentiometric acid base titrations under oxygen and carbon dioxide–free conditions. The data obtained from these titrations was used to calculate the binary and ternary stability constants using the programme HYPERQUAD. The overall stability constants for VO2+-L-Ox system (log β1111 = 18.9, 18.79 and 19.86), VO2+-L-Lact system (log β1111 = 21.83, 20.98 and 22.86), and VO2+-L-Phos system (log β1111 = 27.35, 24.16 and 27.42) (for L= Im4COOH, Im2COOH and MeIm2COOH, respectively) were obtained. The species distribution diagrams showed that under physiological pH the following ternary and quaternary species; [(VO)L(bL)], and [VO(L)(bL)(OH)], would dominate provided that the competition with serum proteins is not too strong. These species were also confirmed by HPLC, LC-MS and EPR. The overall stability constants for the VO2+-L-HSA system (log β2,1,1,0 = 24.3, 23.7 and 24.7), and for the VO2+-L-hTf system (log β2,2,1,0 = 31.1, 30.8, 36.4 for L = Im4COOH, Im2COOH and MeIm2COOH, respectively), suggesting stronger binding of transferrin. The formation constants for the formation of binary (VO(IV) and the proteins) were 9.1 and 13 for log β11, and 20.9 and 25.2 for β12, for human serum albumin and human serum transferrin respectively. The species distribution diagrams for the proteins (HMM) with oxidovanadium(IV) under physiological pH was dominated by VO(HMM)2, VOL(HMM) for unsubstituted Im4COOH and Im2COOH, however, for the N-substituted MeIm2COOH, the species distribution diagrams under physiological pH, were dominated by VOL2, VO(HMM)2 and VO2L2(HMM). These species were further confirmed by HPLC, MALDI-TOF-MS and EPR. The glucose stimulated insulin secretion (GSIS) action of the complexes was investigated using INS-1E cells at 1μM concentration which was established through cytotoxicity studies via the MTT assay. The vanadium salt (VOSO4), cationic vanadium(IV) complex ([VO(MeImCH2OH)2]2+) were also included in the GSIS study in addition to the three neutral complexes [VO(Im4COO)2, VO(Im2COO)2 and VO(MeIm2COO)2] for comparison. The neutral complexes, especially VO(MeIm2COO)2, showed promising results in the stimulation of insulin secretion than the cationic complex and the vanadium salt.
- Full Text:
- Date Issued: 2014
Causal determinants of the public's attitudes towards hunting as a basis for strategies to improve the social legitimacy of hunting
- Coetzer, Wentzel Christoffel
- Authors: Coetzer, Wentzel Christoffel
- Date: 2014
- Subjects: Hunting -- South Africa , Wildlife management -- South Africa , Wildlife conservation -- South Africa
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10759 , http://hdl.handle.net/10948/d1021164
- Description: It is widely acknowledged that the organised wildlife and hunting industry in South Africa contributes significantly to the country’s economy, as well as to the effective management and conservation of wildlife on privately owned land. Despite this, hunting has come under increasing attack by anti-hunting proponents who wish to bring a ban on hunting. A number of broad shifts across society at large and lobbying against hunting by anti-hunting proponents have given rise to legitimate concerns regarding the social acceptability of hunting. To maintain the social legitimacy of hunting, it is imperative to put strategies in place to actively broaden the base of public acceptance of hunting. Towards this aim, this study is an empirical investigation of the causal determinants of the public’s attitudes towards hunting and of the implications it holds for improving the social legitimacy of hunting. The study commenced by building a sound theoretical foundation from the available literature on the measurement of attitudes, the structure and formation of attitudes, the instrumental and experiential aspects of attitudes, attitudinal ambivalence, the psychology of strong attitudes, as well as the phenomenon of cognitive dissonance. Thereafter, the study turned to identify an adequate and empirically valid research approach for investigating attitudes and its causal determinants. A popular attitude theory in social psychology, namely the theory of reasoned action, was identified as a suitable conceptual framework for conducting this study. According to the reasoned action model, the salient behavioural beliefs people associate with a particular behaviour form the informational foundation (or cognitive foundation) on which their attitudes towards the behaviour are based. More specifically, the model suggests that peoples’ overall attitude towards a behaviour is a function of their perceived probability that a behaviour will produce certain outcomes (belief strength), as well as the degree to which they judge the perceived outcomes of the behaviour as positive or negative (outcome evaluation). The methodological design of the study’s empirical component was strictly based on the standard procedures prescribed by the theory of reasoned action. Two consecutive and methodologically interrelated surveys were conducted amongst members of the public to collect the study’s primary data. The main salient behavioural beliefs on which different attitudes towards hunting are based were identified and further investigated. The results were analysed from the perspective of the theory of reasoned action and a clear understanding of the causal determinants of different attitudes towards hunting were attained. Based on the findings of the study, a number of conclusions and recommendations were made that may guide the development of future strategies to improve the social legitimacy of hunting. Amongst other things, it was suggested that public education programmes should be developed to address the public’s misconceptions of hunting; that public relation campaigns be undertaken to improve the public’s negative image of hunters; and that hunter education programmes be put in place to make hunters aware of the role they could play at community level to improve the social acceptability of hunting. Detailed guidelines regarding the contents of such education programmes and public relation campaigns were provided.
- Full Text:
- Date Issued: 2014
- Authors: Coetzer, Wentzel Christoffel
- Date: 2014
- Subjects: Hunting -- South Africa , Wildlife management -- South Africa , Wildlife conservation -- South Africa
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10759 , http://hdl.handle.net/10948/d1021164
- Description: It is widely acknowledged that the organised wildlife and hunting industry in South Africa contributes significantly to the country’s economy, as well as to the effective management and conservation of wildlife on privately owned land. Despite this, hunting has come under increasing attack by anti-hunting proponents who wish to bring a ban on hunting. A number of broad shifts across society at large and lobbying against hunting by anti-hunting proponents have given rise to legitimate concerns regarding the social acceptability of hunting. To maintain the social legitimacy of hunting, it is imperative to put strategies in place to actively broaden the base of public acceptance of hunting. Towards this aim, this study is an empirical investigation of the causal determinants of the public’s attitudes towards hunting and of the implications it holds for improving the social legitimacy of hunting. The study commenced by building a sound theoretical foundation from the available literature on the measurement of attitudes, the structure and formation of attitudes, the instrumental and experiential aspects of attitudes, attitudinal ambivalence, the psychology of strong attitudes, as well as the phenomenon of cognitive dissonance. Thereafter, the study turned to identify an adequate and empirically valid research approach for investigating attitudes and its causal determinants. A popular attitude theory in social psychology, namely the theory of reasoned action, was identified as a suitable conceptual framework for conducting this study. According to the reasoned action model, the salient behavioural beliefs people associate with a particular behaviour form the informational foundation (or cognitive foundation) on which their attitudes towards the behaviour are based. More specifically, the model suggests that peoples’ overall attitude towards a behaviour is a function of their perceived probability that a behaviour will produce certain outcomes (belief strength), as well as the degree to which they judge the perceived outcomes of the behaviour as positive or negative (outcome evaluation). The methodological design of the study’s empirical component was strictly based on the standard procedures prescribed by the theory of reasoned action. Two consecutive and methodologically interrelated surveys were conducted amongst members of the public to collect the study’s primary data. The main salient behavioural beliefs on which different attitudes towards hunting are based were identified and further investigated. The results were analysed from the perspective of the theory of reasoned action and a clear understanding of the causal determinants of different attitudes towards hunting were attained. Based on the findings of the study, a number of conclusions and recommendations were made that may guide the development of future strategies to improve the social legitimacy of hunting. Amongst other things, it was suggested that public education programmes should be developed to address the public’s misconceptions of hunting; that public relation campaigns be undertaken to improve the public’s negative image of hunters; and that hunter education programmes be put in place to make hunters aware of the role they could play at community level to improve the social acceptability of hunting. Detailed guidelines regarding the contents of such education programmes and public relation campaigns were provided.
- Full Text:
- Date Issued: 2014
Characterization of animal fibres
- Authors: Notayi, Mzwamadoda
- Date: 2014
- Subjects: Animal fibres , Textile fabrics , Animal science
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10552 , http://hdl.handle.net/10948/d1020426
- Description: Identification of fibres, particularly in blends, requires knowledge of their characteristics. Individual Identifying features between wool and mohair fibres were investigated in this study using a Scanning Electron Microscope (SEM), Fourier Transform Infrared-Attenuated Total Reflection (FTIR-ATR), Fourier Transform Raman and Atomic Force Microscope (AFM). This study confirmed that wool and mohair can be differentiated and identified in blends using the cuticle scale height (CSH) criterion, wool having an average CSH of 0.6 ± 0.1 μm and mohair having an average CSH of 0.4 ± 0.1 μm. The AFM provided highly reproducible CSH results, which also confirmed the SEM results that indeed wool and mohair could be differentiated using the CSH as criterion. The AFM gave a CSH value of 0.9 ± 0.2 μm for wool and 0.6 ± 0.2 μm for mohair, the difference between the two results being statistically significant according to the student t-test. It has been demonstrated that wool and mohair identification in blends is possible, by using the AFM to measure CSH, although the method is very time consuming and might be expensive. The FTIR-ATR showed similar spectra for wool and mohair fibres, confirming that the two fibre types consist of the same polymer material. Nevertheless, a difference was observed in the ratios of the relative intensities of the amide I (around 1630 cm-1) to the amide II (around 1515cm-1) absorption bands. The FT Raman provided similar spectra for the wool and mohair fibres, although a possible distinguishing feature between the two fibres could be the intensities of the alkyl side chains chemical band near 2940 cm-1 in the spectra of the two fibre types. According to the results obtained in this study, the FTIR-ATR and the FT Raman techniques may have potential for differentiating between wool and mohair but this requires further investigation.
- Full Text:
- Date Issued: 2014
- Authors: Notayi, Mzwamadoda
- Date: 2014
- Subjects: Animal fibres , Textile fabrics , Animal science
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10552 , http://hdl.handle.net/10948/d1020426
- Description: Identification of fibres, particularly in blends, requires knowledge of their characteristics. Individual Identifying features between wool and mohair fibres were investigated in this study using a Scanning Electron Microscope (SEM), Fourier Transform Infrared-Attenuated Total Reflection (FTIR-ATR), Fourier Transform Raman and Atomic Force Microscope (AFM). This study confirmed that wool and mohair can be differentiated and identified in blends using the cuticle scale height (CSH) criterion, wool having an average CSH of 0.6 ± 0.1 μm and mohair having an average CSH of 0.4 ± 0.1 μm. The AFM provided highly reproducible CSH results, which also confirmed the SEM results that indeed wool and mohair could be differentiated using the CSH as criterion. The AFM gave a CSH value of 0.9 ± 0.2 μm for wool and 0.6 ± 0.2 μm for mohair, the difference between the two results being statistically significant according to the student t-test. It has been demonstrated that wool and mohair identification in blends is possible, by using the AFM to measure CSH, although the method is very time consuming and might be expensive. The FTIR-ATR showed similar spectra for wool and mohair fibres, confirming that the two fibre types consist of the same polymer material. Nevertheless, a difference was observed in the ratios of the relative intensities of the amide I (around 1630 cm-1) to the amide II (around 1515cm-1) absorption bands. The FT Raman provided similar spectra for the wool and mohair fibres, although a possible distinguishing feature between the two fibres could be the intensities of the alkyl side chains chemical band near 2940 cm-1 in the spectra of the two fibre types. According to the results obtained in this study, the FTIR-ATR and the FT Raman techniques may have potential for differentiating between wool and mohair but this requires further investigation.
- Full Text:
- Date Issued: 2014
Characterization of chromatic dispersion in single mode fibre
- Authors: Wassin, Shukree
- Date: 2014
- Subjects: Fiber optics Electromagnetic waves , Electromagnetic waves -- Transmission
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47807 , vital:40379
- Description: In this dissertation, an investigation of chromatic dispersion is presented. The Pulse delay and phase Shift chromatic dispersion characterization techniques were used for conducting the measurements. The experiments were performed in a modern optical fibre research laboratory and chromatic dispersion measurements were carried out on several lengths of G.652 and G.655 single mode fibres. The pulse delay characterization technique measures the time of flight between two modulated optical signals whilst propagating along the fibre under test. During phase shift experiments, the group delay is obtained by measuring the relative phase difference as a function of wavelength, between adjacent sinusoidal light signals. The pulse delay and phase shift characterization techniques illustrated excellent agreement in the measured! chromatic Dispersion coefficients along the G.652 standard single mode! fibre as well as the G.655 positive and negative non-zero dispersion shifted fibre. It was found that the measurement accuracy improved as the fibre length increased. A periodic shift between the modulated optical signals, propagating along the fibre was experimentally observed. It is to be remarked that the longer wavelength signals propagated faster along the G.655 positive non-zero dispersion shifted fibre in comparison to its transmission within the G.655 negative non-zero dispersion shifted fibre. Furthermore, it was found that the sinusoidal signal shifted towards the left along the G.655 negative NZDSF fibre whilst the shift occurred towards the right along the G.655 positive NZDSF fibre. Generally, the shift arising along the G.655 fibres was found to be smaller than the shift seen throughout the G.652 fibres. Towards the end of this study, a chromatic dispersion compensation system was designed and tested. Once characterization of the compensation link was completed, it was experimentally illustrated that the chromatic dispersion across the system was successfully reduced. Finally, a sum of squares of error statistical test showed that the phase shift technique is more accurate in comparison to the pulse delay method. This result was found to be in good agreement with published work found in literature.
- Full Text:
- Date Issued: 2014
- Authors: Wassin, Shukree
- Date: 2014
- Subjects: Fiber optics Electromagnetic waves , Electromagnetic waves -- Transmission
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47807 , vital:40379
- Description: In this dissertation, an investigation of chromatic dispersion is presented. The Pulse delay and phase Shift chromatic dispersion characterization techniques were used for conducting the measurements. The experiments were performed in a modern optical fibre research laboratory and chromatic dispersion measurements were carried out on several lengths of G.652 and G.655 single mode fibres. The pulse delay characterization technique measures the time of flight between two modulated optical signals whilst propagating along the fibre under test. During phase shift experiments, the group delay is obtained by measuring the relative phase difference as a function of wavelength, between adjacent sinusoidal light signals. The pulse delay and phase shift characterization techniques illustrated excellent agreement in the measured! chromatic Dispersion coefficients along the G.652 standard single mode! fibre as well as the G.655 positive and negative non-zero dispersion shifted fibre. It was found that the measurement accuracy improved as the fibre length increased. A periodic shift between the modulated optical signals, propagating along the fibre was experimentally observed. It is to be remarked that the longer wavelength signals propagated faster along the G.655 positive non-zero dispersion shifted fibre in comparison to its transmission within the G.655 negative non-zero dispersion shifted fibre. Furthermore, it was found that the sinusoidal signal shifted towards the left along the G.655 negative NZDSF fibre whilst the shift occurred towards the right along the G.655 positive NZDSF fibre. Generally, the shift arising along the G.655 fibres was found to be smaller than the shift seen throughout the G.652 fibres. Towards the end of this study, a chromatic dispersion compensation system was designed and tested. Once characterization of the compensation link was completed, it was experimentally illustrated that the chromatic dispersion across the system was successfully reduced. Finally, a sum of squares of error statistical test showed that the phase shift technique is more accurate in comparison to the pulse delay method. This result was found to be in good agreement with published work found in literature.
- Full Text:
- Date Issued: 2014
Comparison of the population growth potential of South African loggerhead (Caretta caretta) and leatherback (Dermochelys coriacea) sea turtles
- Authors: Tucek, Jenny Bianka
- Date: 2014
- Subjects: Sea turtles -- Population viability analysis -- South Africa , Migratory animals -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/5032 , vital:20793
- Description: A beach conservation programme protecting nesting loggerhead (Caretta caretta) and leatherback (Dermochelys coriacea) sea turtles in South Africa was started in 1963. As initial numbers of nesting females were low for both species (107 loggerheads and 24 leatherbacks) it was proposed that the protection of eggs, hatchlings and nesting females along the nesting beach would induce population growth and prohibit local extinction. Today, 50 years later, the loggerhead population exceeds 650 females per annum, whereas the leatherback population counts about 65 nesting females per year. The trend for leatherback turtles is that the population has been stable for about 30 years whereas loggerheads are increasing exponentially. Thus, this thesis investigated several life-history traits to explain the differing responses to the ongoing beach conservation programme. Reproductive output and success were assessed for both species; it was hypothesised that environmental conditions are sub-optimal for leatherback turtles to reproduce successfully. It was ascertained that nesting loggerhead females deposit larger clutches than leatherbacks (112 ± SD 20 eggs and 100 ± SD 23 eggs, respectively), but that annual reproductive output per individual leatherback female exceeds that of loggerhead turtles (±700 eggs and ±448 eggs, respectively) because they exhibit a higher intra-seasonal nesting frequency (leatherbacks n = 7 and loggerheads n = 4 from Nel et al. 2013). Emergence success (i.e. the percentage of hatchlings produced) per nest was similar for both species (loggerhead 73.6 ± SD 27.68 % and leatherback turtles 73.8 ± SD 22.70 %), but as loggerhead turtles nest in greater numbers, i.e. producing more hatchlings per year, the absolute population growth potential favours the loggerhead turtle. The second factor investigated was sex ratio because sea turtles display temperature-dependent sex determination (TSD) where extreme incubation temperatures can skew the sex ratio (i.e. feminising or masculinising a clutch). It was suspected that leatherback turtles are male-biased as this is the southern-most rookery (for both species). Further, leatherback nests are generally closer to the high tide mark, which might induce a cooling effect. Standard histological techniques were applied to sex hatchlings and a generalized linear model (GLM) was used to approximate annual sex ratio. Loggerhead sex ratio (2009 - 2011) was estimated at 86.9 ± SE 0.35 % female-biased; however, sufficient replication for the leatherback population was only obtained for season 2010, which indicated a 97.1 % (95 % CI 93.3 - 98.7) female bias. Both species are, thus, highly female-biased, and current sex ratio for leatherback turtles is not prohibiting population growth. Current sex ratios, however, are not necessarily indicative of sex ratios in the past which would have induced present population growth. Thus, to account for present population growth profiles, sex ratios from the past needed to be ascertained. Annual sex ratios (1997 - 2011) were modelled from historical air and sea surface temperatures (SSTs) but no significant change over time was obtained for either loggerhead or leatherback turtles (linear regression; p ≥ 0.45). The average sex ratio over this 15-year period for the South African loggerhead turtle was approximated at 77.1 ± SE 3.36 % female-biased, whereas leatherbacks exhibited a 99.5 ± SE 0.24 % female bias. Re-analysing data from the mid-80s by Maxwell et al. (1988) also indicated a 77.4 % female bias for the South African loggerhead population. It is, therefore, highly likely that sex ratios of the South African loggerhead and leatherback sea turtle populations have been stable for at least three decades and are not accountable for the differing population growth profiles as they are displayed today. Another possibility that could explain the opposed population growth profiles is the time taken for animals to replace themselves, i.e. age at maturity. It was suspected that age at maturity for the South African loggerhead turtle is comparable with that for leatherbacks. Using data from a 30-year mutilation tagging experiment (i.e. notching), age at first reproduction for South African loggerhead females was estimated. Results ranged broadly but a mean of 36.2 ± SD 7.71 years was obtained using a Gaussian distribution. Age at reproduction of the South African leatherback turtle was not determined but the literature suggests a much younger age of 13.3 - 26.8 years (Zug & Parham 1996, Dutton et al. 2005, Avens et al. 2009, Jones et al. 2011). Therefore, population growth would favour leatherback turtles as they exhibit a much shorter generation time. Finally, it was concluded that all life-history parameters investigated favour leatherback turtles, yet loggerheads are displaying population growth. However, as there were no obvious constraints to population growth on the nesting beach, it is suspected that population growth of the South African leatherback turtle is either unobserved (due to inadequate monitoring not capturing sufficient numbers of nesting events to establish a trend) or that population growth is prohibited by some offshore factor such as industrial fisheries (or some other driver not yet identified). Monitoring should, thus, be expanded and offshore mortality monitored as the leatherback population nesting in South Africa is still critically endangered with nesting numbers dangerously low.
- Full Text:
- Date Issued: 2014
- Authors: Tucek, Jenny Bianka
- Date: 2014
- Subjects: Sea turtles -- Population viability analysis -- South Africa , Migratory animals -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/5032 , vital:20793
- Description: A beach conservation programme protecting nesting loggerhead (Caretta caretta) and leatherback (Dermochelys coriacea) sea turtles in South Africa was started in 1963. As initial numbers of nesting females were low for both species (107 loggerheads and 24 leatherbacks) it was proposed that the protection of eggs, hatchlings and nesting females along the nesting beach would induce population growth and prohibit local extinction. Today, 50 years later, the loggerhead population exceeds 650 females per annum, whereas the leatherback population counts about 65 nesting females per year. The trend for leatherback turtles is that the population has been stable for about 30 years whereas loggerheads are increasing exponentially. Thus, this thesis investigated several life-history traits to explain the differing responses to the ongoing beach conservation programme. Reproductive output and success were assessed for both species; it was hypothesised that environmental conditions are sub-optimal for leatherback turtles to reproduce successfully. It was ascertained that nesting loggerhead females deposit larger clutches than leatherbacks (112 ± SD 20 eggs and 100 ± SD 23 eggs, respectively), but that annual reproductive output per individual leatherback female exceeds that of loggerhead turtles (±700 eggs and ±448 eggs, respectively) because they exhibit a higher intra-seasonal nesting frequency (leatherbacks n = 7 and loggerheads n = 4 from Nel et al. 2013). Emergence success (i.e. the percentage of hatchlings produced) per nest was similar for both species (loggerhead 73.6 ± SD 27.68 % and leatherback turtles 73.8 ± SD 22.70 %), but as loggerhead turtles nest in greater numbers, i.e. producing more hatchlings per year, the absolute population growth potential favours the loggerhead turtle. The second factor investigated was sex ratio because sea turtles display temperature-dependent sex determination (TSD) where extreme incubation temperatures can skew the sex ratio (i.e. feminising or masculinising a clutch). It was suspected that leatherback turtles are male-biased as this is the southern-most rookery (for both species). Further, leatherback nests are generally closer to the high tide mark, which might induce a cooling effect. Standard histological techniques were applied to sex hatchlings and a generalized linear model (GLM) was used to approximate annual sex ratio. Loggerhead sex ratio (2009 - 2011) was estimated at 86.9 ± SE 0.35 % female-biased; however, sufficient replication for the leatherback population was only obtained for season 2010, which indicated a 97.1 % (95 % CI 93.3 - 98.7) female bias. Both species are, thus, highly female-biased, and current sex ratio for leatherback turtles is not prohibiting population growth. Current sex ratios, however, are not necessarily indicative of sex ratios in the past which would have induced present population growth. Thus, to account for present population growth profiles, sex ratios from the past needed to be ascertained. Annual sex ratios (1997 - 2011) were modelled from historical air and sea surface temperatures (SSTs) but no significant change over time was obtained for either loggerhead or leatherback turtles (linear regression; p ≥ 0.45). The average sex ratio over this 15-year period for the South African loggerhead turtle was approximated at 77.1 ± SE 3.36 % female-biased, whereas leatherbacks exhibited a 99.5 ± SE 0.24 % female bias. Re-analysing data from the mid-80s by Maxwell et al. (1988) also indicated a 77.4 % female bias for the South African loggerhead population. It is, therefore, highly likely that sex ratios of the South African loggerhead and leatherback sea turtle populations have been stable for at least three decades and are not accountable for the differing population growth profiles as they are displayed today. Another possibility that could explain the opposed population growth profiles is the time taken for animals to replace themselves, i.e. age at maturity. It was suspected that age at maturity for the South African loggerhead turtle is comparable with that for leatherbacks. Using data from a 30-year mutilation tagging experiment (i.e. notching), age at first reproduction for South African loggerhead females was estimated. Results ranged broadly but a mean of 36.2 ± SD 7.71 years was obtained using a Gaussian distribution. Age at reproduction of the South African leatherback turtle was not determined but the literature suggests a much younger age of 13.3 - 26.8 years (Zug & Parham 1996, Dutton et al. 2005, Avens et al. 2009, Jones et al. 2011). Therefore, population growth would favour leatherback turtles as they exhibit a much shorter generation time. Finally, it was concluded that all life-history parameters investigated favour leatherback turtles, yet loggerheads are displaying population growth. However, as there were no obvious constraints to population growth on the nesting beach, it is suspected that population growth of the South African leatherback turtle is either unobserved (due to inadequate monitoring not capturing sufficient numbers of nesting events to establish a trend) or that population growth is prohibited by some offshore factor such as industrial fisheries (or some other driver not yet identified). Monitoring should, thus, be expanded and offshore mortality monitored as the leatherback population nesting in South Africa is still critically endangered with nesting numbers dangerously low.
- Full Text:
- Date Issued: 2014
Contemporary use and seasonal abundance of indigenous edible plants (with an emphasis on geophytes) available to human foragers on the Cape south coast, South Africa
- Authors: De Vynck, Jan Carlo
- Date: 2014
- Subjects: Wild plants, Edible -- Africa, Southern , Coastal plants -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10638 , http://hdl.handle.net/10948/d1020044
- Description: Human subsistence within the Cape Floristic Region (Cape) dates back to our inception as a distinct species. Unique archaeological evidence found here for the defining attribute of cognitive modernity, as well as coinciding paleo-climatic challenges to survival, both highlight the Cape’s potential to support the existence of pre-historic hunter-gatherers. This habitat, with its unprecedented diversity of geophytes and other plant growth forms, has not yet revealed its potential to provide carbohydrate resources for early Homo sapiens sapiens. In order to investigate this potential, an ethnobotanical survey of the south Cape coastal area near Still Bay was conducted. Despite 17th Century colonialism marking the onset of indigenous plant knowledge decline, the 18 people of Khoe-San descent interviewed in this survey still actively used 58 indigenous edible plant species with a variety of 69 uses. Fruit showed the highest popularity of plants used (52 percent) followed by nectar, with plants having underground storage organs (USOs) ranking third (34 percent). Among growth forms, shrubs dominated (34 percent) followed by geophytes and trees (both 21 percent). With the exception of Prionium serratum, which was rare in the research area, this study failed to identify species that could have formed a staple source of carbohydrate for pre-colonial Khoe-San peoples of the Cape south coast. While eight species of USOs were identified (12 percent of total) only Cyphia species emerged as an important carbohydrate source. This study indicated the importance of Thicket Biome species as a source of edible plants. The second component of the study comprised a two year phenological survey of indigenous edible plant species in four primary vegetation types. A total of 32 USO species and 21 species with aboveground edible carbohydrates (fruiting species) were identified across all sites. Limestone Fynbos had the richest flora of edible species (21 USO species and 18 fruiting species), followed by Strandveld (15 USOs and 13 fruiting species), Renosterveld (8 and 8, respectively) and lastly Sand Fynbos (5 and 5, respectively). The season of highest apparency showed slight variation amongst the four sites over the two years, with more variation evident in the period of apparency. The first survey year had below average rainfall, while the second year received an average rainfall amount. The second year saw a dramatic increase in apparency of abundance for all sites (50 to 60 percent increase) except for the Sand Fynbos site, which showed little change. The other sites showed a one month increase in the period of apparency in the second survey year. Overall, late summer to autumn was the period of lowest apparency of USOs. The ripening of certain fruiting species during this time would have provided a source of carbohydrate when USO availability was at its lowest. Strandveld had the highest biomass in the peak of apparency (over 80 kgha-1) in the first year with a nearly 20 percent increase for the second year. The combined biomass for the four study sites in the first survey year was roughly 150 kgha-1 and 185 kgha-1 for the second year. The apparency of abundance (ripe and edible phase) of fruiting species did not increase much for Renosterveld and Strandveld in the second survey year, except for Limestone Fynbos (49 percent increase) and Sand Fynbos (53 percent). A multivariate analysis showed seven phenophases for high apparency of edible USOs and ripe fruit across the four vegetation types. Given the contribution of evergreen USOs and fruiting species, there would always have been carbohydrates available for foragers to collect in the major vegetation types of the south Cape coast. However, harvesting and processing this carbohydrate resource would have posed cognitive challenges for MSA hunter-gatherers, given the interwoven taxonomic complexity of numerous toxic plant species, and the diverse phenology of edible plant species within the varied vegetation types. These challenges were undoubtedly mastered, highlighting the Cape environment as a possible catalyst to improved human cognitive maturity.
- Full Text:
- Date Issued: 2014
- Authors: De Vynck, Jan Carlo
- Date: 2014
- Subjects: Wild plants, Edible -- Africa, Southern , Coastal plants -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10638 , http://hdl.handle.net/10948/d1020044
- Description: Human subsistence within the Cape Floristic Region (Cape) dates back to our inception as a distinct species. Unique archaeological evidence found here for the defining attribute of cognitive modernity, as well as coinciding paleo-climatic challenges to survival, both highlight the Cape’s potential to support the existence of pre-historic hunter-gatherers. This habitat, with its unprecedented diversity of geophytes and other plant growth forms, has not yet revealed its potential to provide carbohydrate resources for early Homo sapiens sapiens. In order to investigate this potential, an ethnobotanical survey of the south Cape coastal area near Still Bay was conducted. Despite 17th Century colonialism marking the onset of indigenous plant knowledge decline, the 18 people of Khoe-San descent interviewed in this survey still actively used 58 indigenous edible plant species with a variety of 69 uses. Fruit showed the highest popularity of plants used (52 percent) followed by nectar, with plants having underground storage organs (USOs) ranking third (34 percent). Among growth forms, shrubs dominated (34 percent) followed by geophytes and trees (both 21 percent). With the exception of Prionium serratum, which was rare in the research area, this study failed to identify species that could have formed a staple source of carbohydrate for pre-colonial Khoe-San peoples of the Cape south coast. While eight species of USOs were identified (12 percent of total) only Cyphia species emerged as an important carbohydrate source. This study indicated the importance of Thicket Biome species as a source of edible plants. The second component of the study comprised a two year phenological survey of indigenous edible plant species in four primary vegetation types. A total of 32 USO species and 21 species with aboveground edible carbohydrates (fruiting species) were identified across all sites. Limestone Fynbos had the richest flora of edible species (21 USO species and 18 fruiting species), followed by Strandveld (15 USOs and 13 fruiting species), Renosterveld (8 and 8, respectively) and lastly Sand Fynbos (5 and 5, respectively). The season of highest apparency showed slight variation amongst the four sites over the two years, with more variation evident in the period of apparency. The first survey year had below average rainfall, while the second year received an average rainfall amount. The second year saw a dramatic increase in apparency of abundance for all sites (50 to 60 percent increase) except for the Sand Fynbos site, which showed little change. The other sites showed a one month increase in the period of apparency in the second survey year. Overall, late summer to autumn was the period of lowest apparency of USOs. The ripening of certain fruiting species during this time would have provided a source of carbohydrate when USO availability was at its lowest. Strandveld had the highest biomass in the peak of apparency (over 80 kgha-1) in the first year with a nearly 20 percent increase for the second year. The combined biomass for the four study sites in the first survey year was roughly 150 kgha-1 and 185 kgha-1 for the second year. The apparency of abundance (ripe and edible phase) of fruiting species did not increase much for Renosterveld and Strandveld in the second survey year, except for Limestone Fynbos (49 percent increase) and Sand Fynbos (53 percent). A multivariate analysis showed seven phenophases for high apparency of edible USOs and ripe fruit across the four vegetation types. Given the contribution of evergreen USOs and fruiting species, there would always have been carbohydrates available for foragers to collect in the major vegetation types of the south Cape coast. However, harvesting and processing this carbohydrate resource would have posed cognitive challenges for MSA hunter-gatherers, given the interwoven taxonomic complexity of numerous toxic plant species, and the diverse phenology of edible plant species within the varied vegetation types. These challenges were undoubtedly mastered, highlighting the Cape environment as a possible catalyst to improved human cognitive maturity.
- Full Text:
- Date Issued: 2014
Developing an understanding of the drivers of bat activity patterns relevant to wind turbines
- Authors: Thwaits, Tiffany Edan
- Date: 2014
- Subjects: Bats -- Behavior -- Climatic factors -- South Africa , Bats -- Ecology -- South Africa -- Eastern Cape , Wind power -- Environmental aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10726 , http://hdl.handle.net/10948/d1020970
- Description: The increasing number of proposed wind farm developments in South Africa provides an immediate reason to assess bat activity and diversity, with the expectation of developing measures to mitigate for negative impacts. The overall aim of this thesis was contribute to an understanding of the drivers of bat activity, relevant to wind turbines, and to determine what factors (exogenous – environmental, or endogenous – intrinsic physiological processes) contributed to observed bat activity patterns, at the Metrowind Van Stadens Wind Farm in the Eastern Cape of South Africa. A combination of active (mist netting) and passive (acoustic) bat monitoring techniques were used to determine free-ranging bat activity patterns (Chapter 3). A total of 889 bat passes were recorded over 323 detector nights from the beginning of May 2012 to the end of December 2012. The Cape serotine bat (82 per cent) and the Egyptian free-tailed bat (97 per cent) made up the majority of all bat passes recorded on site. Large variations in bat activity per month and per hour were apparent, with bat activity peaking in May 2012 and during the first few hours after sunset (18:00-23:00). Patterns in nightly, free-ranging bat activity at the site were modelled against various environmental conditions. Month, temperature, wind speed and an interaction between month and rainfall were the most significant predictors of bat activity, explaining 80 per cent of the variation observed on free-ranging bat activity patterns. A total of eight Cape serotine bats (Table 4.1.) were caught in mist nets on site and changes in the resting metabolic rate (RMR) of torpid (n = 6), and normothermic (n = 2) bats, over a 24 hr period, were measured and used to predict free-ranging Cape serotine bat activity (Chapter 4). Cape serotine bats showed a high proclivity for torpor in the laboratory and peaks in RMR were observed at 18:00 (0.89 ± 0.95 VO2 mℓ.g-1.hr-1) and again from 20:00-21:00 (0.89 ± 0.91 VO2 mℓ.g-1.hr-1). Peaks in RMR of torpid individuals coincided with peaks in the average hourly free-ranging activity of the Cape serotine bat, and RMR explained 33 per cent of the variation and was a good predictor of free-ranging bat activity (R2 = 0.2914). This study showed that both exogenous (Chapter 3) and endogenous (Chapter 4) factors drive bat activity in the wild. Although this dissertation was not intended for wind turbine management, the information presented on the biology and activity of bats is important for managing interactions between bats and wind turbines. By determining what factors influence bat activity, we are able to predict when bats will be most active and thus can develop mitigation measures to reduce the potential impacts that wind turbines will have on the bat community. In order to conserve bats and reduce potential bat fatalities from occurring at the site, mitigation measures should be concentrated to those times when bats are most active (May and during the first few hours after sunset – 18:00 to 22:00).
- Full Text:
- Date Issued: 2014
- Authors: Thwaits, Tiffany Edan
- Date: 2014
- Subjects: Bats -- Behavior -- Climatic factors -- South Africa , Bats -- Ecology -- South Africa -- Eastern Cape , Wind power -- Environmental aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10726 , http://hdl.handle.net/10948/d1020970
- Description: The increasing number of proposed wind farm developments in South Africa provides an immediate reason to assess bat activity and diversity, with the expectation of developing measures to mitigate for negative impacts. The overall aim of this thesis was contribute to an understanding of the drivers of bat activity, relevant to wind turbines, and to determine what factors (exogenous – environmental, or endogenous – intrinsic physiological processes) contributed to observed bat activity patterns, at the Metrowind Van Stadens Wind Farm in the Eastern Cape of South Africa. A combination of active (mist netting) and passive (acoustic) bat monitoring techniques were used to determine free-ranging bat activity patterns (Chapter 3). A total of 889 bat passes were recorded over 323 detector nights from the beginning of May 2012 to the end of December 2012. The Cape serotine bat (82 per cent) and the Egyptian free-tailed bat (97 per cent) made up the majority of all bat passes recorded on site. Large variations in bat activity per month and per hour were apparent, with bat activity peaking in May 2012 and during the first few hours after sunset (18:00-23:00). Patterns in nightly, free-ranging bat activity at the site were modelled against various environmental conditions. Month, temperature, wind speed and an interaction between month and rainfall were the most significant predictors of bat activity, explaining 80 per cent of the variation observed on free-ranging bat activity patterns. A total of eight Cape serotine bats (Table 4.1.) were caught in mist nets on site and changes in the resting metabolic rate (RMR) of torpid (n = 6), and normothermic (n = 2) bats, over a 24 hr period, were measured and used to predict free-ranging Cape serotine bat activity (Chapter 4). Cape serotine bats showed a high proclivity for torpor in the laboratory and peaks in RMR were observed at 18:00 (0.89 ± 0.95 VO2 mℓ.g-1.hr-1) and again from 20:00-21:00 (0.89 ± 0.91 VO2 mℓ.g-1.hr-1). Peaks in RMR of torpid individuals coincided with peaks in the average hourly free-ranging activity of the Cape serotine bat, and RMR explained 33 per cent of the variation and was a good predictor of free-ranging bat activity (R2 = 0.2914). This study showed that both exogenous (Chapter 3) and endogenous (Chapter 4) factors drive bat activity in the wild. Although this dissertation was not intended for wind turbine management, the information presented on the biology and activity of bats is important for managing interactions between bats and wind turbines. By determining what factors influence bat activity, we are able to predict when bats will be most active and thus can develop mitigation measures to reduce the potential impacts that wind turbines will have on the bat community. In order to conserve bats and reduce potential bat fatalities from occurring at the site, mitigation measures should be concentrated to those times when bats are most active (May and during the first few hours after sunset – 18:00 to 22:00).
- Full Text:
- Date Issued: 2014
Development of a bulbine frutescens and carpobrotus edulis cream in collaboration with african traditional healers of the Nelson Mandela Metropole
- Authors: Keele, Mbali Zamathiyane
- Date: 2014
- Subjects: Drug development -- South Africa -- Port Elizabeth , Healers -- South Africa -- Port Elizabeth , Traditional medicine -- South Africa -- Port Elizabeth , Physicians -- Health -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10358 , http://hdl.handle.net/10948/d1021016
- Description: Collaborations between researchers and African traditional healers on medicinal plants need to go beyond the flow of information from African traditional healers to researchers. Mutual beneficiation wherein African traditional healers reap rewards due to the information they possess is necessary and has been legislated in South Africa. The manner in which such beneficiation occurs and how it will be distributed should be subject to negotiation between (a) the researchers and holders of indigenous knowledge and (b) among holders of indigenous knowledge themselves. Beneficiation can be in the form of access to information, monetary or through shares in commercialised products, amongst others. African traditional healers involved in the collaboration with researchers of the Department of Biochemistry and Microbiology and the Department of Pharmacy at the Nelson Mandela Metropolitan University beneficiated by having access to knowledge and medicinal plants cultivated in the medicinal garden. Beneficiation was expected to extend to monetary gains from the sale of sewn garments and plants from a medicinal plants nursery which was to be developed and from a herbal topical product which was also to be developed. The aim of this research project was to develop a wound healing herbal cream consisting of Bulbine frutescens and Carpobrotus edulis as active ingredients. B. frutescens demonstrated better wound closure properties when compared to C. edulis and the combined extracts. The scratch assay wound was completely closed after 24 hours at B. frutescens concentrations of 5 μg/ml and 10 μg/ml. B. frutescens was more toxic to 3t3-L1 cells than C. edulis, but it was less toxic than the combined extracts. None of the extracts were toxic to Vero cells and the combined extracts significantly promoted their proliferation. Antibacterial activity of all the extracts was low. C. edulis showed antiviral activity against human herpes simplex virus 1 at 62.5, 125 and 250 μg/ml, while the combined extracts were active at 250 μg/ml. The combined extracts exhibited synergistic antioxidant activity. A reverse phase, gradient, high performance liquid chromatography method was developed and validated and used to conduct quality control tests on the extracts and the finished product. It was concluded that the use of whole chromatographic data instead of common peaks data is best for analysis of medicinal plants. The cream that was developed used buffered cream as the base and was stable at 25 °C/65 percent RH for one month with regard to organoleptic and rheological properties and microbial preservation.
- Full Text:
- Date Issued: 2014
- Authors: Keele, Mbali Zamathiyane
- Date: 2014
- Subjects: Drug development -- South Africa -- Port Elizabeth , Healers -- South Africa -- Port Elizabeth , Traditional medicine -- South Africa -- Port Elizabeth , Physicians -- Health -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10358 , http://hdl.handle.net/10948/d1021016
- Description: Collaborations between researchers and African traditional healers on medicinal plants need to go beyond the flow of information from African traditional healers to researchers. Mutual beneficiation wherein African traditional healers reap rewards due to the information they possess is necessary and has been legislated in South Africa. The manner in which such beneficiation occurs and how it will be distributed should be subject to negotiation between (a) the researchers and holders of indigenous knowledge and (b) among holders of indigenous knowledge themselves. Beneficiation can be in the form of access to information, monetary or through shares in commercialised products, amongst others. African traditional healers involved in the collaboration with researchers of the Department of Biochemistry and Microbiology and the Department of Pharmacy at the Nelson Mandela Metropolitan University beneficiated by having access to knowledge and medicinal plants cultivated in the medicinal garden. Beneficiation was expected to extend to monetary gains from the sale of sewn garments and plants from a medicinal plants nursery which was to be developed and from a herbal topical product which was also to be developed. The aim of this research project was to develop a wound healing herbal cream consisting of Bulbine frutescens and Carpobrotus edulis as active ingredients. B. frutescens demonstrated better wound closure properties when compared to C. edulis and the combined extracts. The scratch assay wound was completely closed after 24 hours at B. frutescens concentrations of 5 μg/ml and 10 μg/ml. B. frutescens was more toxic to 3t3-L1 cells than C. edulis, but it was less toxic than the combined extracts. None of the extracts were toxic to Vero cells and the combined extracts significantly promoted their proliferation. Antibacterial activity of all the extracts was low. C. edulis showed antiviral activity against human herpes simplex virus 1 at 62.5, 125 and 250 μg/ml, while the combined extracts were active at 250 μg/ml. The combined extracts exhibited synergistic antioxidant activity. A reverse phase, gradient, high performance liquid chromatography method was developed and validated and used to conduct quality control tests on the extracts and the finished product. It was concluded that the use of whole chromatographic data instead of common peaks data is best for analysis of medicinal plants. The cream that was developed used buffered cream as the base and was stable at 25 °C/65 percent RH for one month with regard to organoleptic and rheological properties and microbial preservation.
- Full Text:
- Date Issued: 2014
Development of polymer templates for ZnO nanorods
- Authors: Dobson, Stephen Robert
- Date: 2014
- Subjects: Polymers , Semiconductor industry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10556 , http://hdl.handle.net/10948/d1020805
- Description: One of the biggest challenges for the semiconductor industry is the development of nanofabrication techniques that allow for the fabrication of structures on a scale tens of nanometers in size. This provides greater potential functionality at reduced costs. Established conventional techniques, such as photolithography, are unable to achieve features below 30 nm due to the inherent limitations of the wavelength of light sources currently available. For this reason block copolymers received considerable attention in order to overcome these challenges in lithographic technology. Block copolymers have an inherent processing advantage of self assembling into various nanoscopic structures such as spheres, cylinders and lamellae amongst others on a scale below 50 nm. The dimensions and structures are readily tuneable based on molecular weights (Mw) and compositions of the copolymers. However, to be usable within industry a great deal more research still needs to be conducted on the use and nature of block copolymers. In this study the block copolymer of poly(styrene-block-methylmethacrylate) (PS-b-PMMA) was investigated as a potential nano-mask for semiconductor growth. Research was conducted on thin films of PS-b-PMMA by altering the parameters influencing the kinetics and thermodynamic effects on the thin films, in order to produce a structure of cylinders of PMMA perpendicular to the substrate within a PS matrix on a silicon (Si) substrate. It is shown that thermally annealing the PS-b-PMMA thin films under conditions where there is no preferential interaction of the substrate or open surface with either components of the block copolymer (i.e. PS or PMMA with Si or ambient) and at an appropriate thin film thickness, perpendicular cylinders of PMMA within a PS matrix form in the thin films. The determined ideal thin film thickness is 32 nm, with non-preferential interaction attained between block and substrate by coating a poly(styrene-random-methylmethacrylate) (PS-r-PMMA) on the Si substrate and annealing within a vacuum. Additionally, acetic acid, as a known selective solvent of PMMA, is used to further process the thin film of PS-b-PMMA. Thus a final PS nano-mask containing pores with a diameter tens of nanometers in size is produced. The pores are shown to have an average diameter of 13.5 nm. Measurements were taken throughout the investigation using a scanning probe microscope (SPM) to determine surface topography and phase morphology of the PS-b-PMMA thin films. X-ray reflectometry (XRR) is used to measure film thickness. The research in this study shows that thin films of PS containing hexagonally arranged pores can be produced and could find potential use as a nano-mask for semiconductor growth.
- Full Text:
- Date Issued: 2014
- Authors: Dobson, Stephen Robert
- Date: 2014
- Subjects: Polymers , Semiconductor industry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10556 , http://hdl.handle.net/10948/d1020805
- Description: One of the biggest challenges for the semiconductor industry is the development of nanofabrication techniques that allow for the fabrication of structures on a scale tens of nanometers in size. This provides greater potential functionality at reduced costs. Established conventional techniques, such as photolithography, are unable to achieve features below 30 nm due to the inherent limitations of the wavelength of light sources currently available. For this reason block copolymers received considerable attention in order to overcome these challenges in lithographic technology. Block copolymers have an inherent processing advantage of self assembling into various nanoscopic structures such as spheres, cylinders and lamellae amongst others on a scale below 50 nm. The dimensions and structures are readily tuneable based on molecular weights (Mw) and compositions of the copolymers. However, to be usable within industry a great deal more research still needs to be conducted on the use and nature of block copolymers. In this study the block copolymer of poly(styrene-block-methylmethacrylate) (PS-b-PMMA) was investigated as a potential nano-mask for semiconductor growth. Research was conducted on thin films of PS-b-PMMA by altering the parameters influencing the kinetics and thermodynamic effects on the thin films, in order to produce a structure of cylinders of PMMA perpendicular to the substrate within a PS matrix on a silicon (Si) substrate. It is shown that thermally annealing the PS-b-PMMA thin films under conditions where there is no preferential interaction of the substrate or open surface with either components of the block copolymer (i.e. PS or PMMA with Si or ambient) and at an appropriate thin film thickness, perpendicular cylinders of PMMA within a PS matrix form in the thin films. The determined ideal thin film thickness is 32 nm, with non-preferential interaction attained between block and substrate by coating a poly(styrene-random-methylmethacrylate) (PS-r-PMMA) on the Si substrate and annealing within a vacuum. Additionally, acetic acid, as a known selective solvent of PMMA, is used to further process the thin film of PS-b-PMMA. Thus a final PS nano-mask containing pores with a diameter tens of nanometers in size is produced. The pores are shown to have an average diameter of 13.5 nm. Measurements were taken throughout the investigation using a scanning probe microscope (SPM) to determine surface topography and phase morphology of the PS-b-PMMA thin films. X-ray reflectometry (XRR) is used to measure film thickness. The research in this study shows that thin films of PS containing hexagonally arranged pores can be produced and could find potential use as a nano-mask for semiconductor growth.
- Full Text:
- Date Issued: 2014
Efficacy of two medical plant extracts and metformin in the prevention of diet induced fatty liver
- Tshidino, Shonisani Cathphonia
- Authors: Tshidino, Shonisani Cathphonia
- Date: 2014
- Subjects: Plant Extracts -- Therapeutic use , Medicinal plants
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/9066 , vital:26461
- Description: Non‐alcoholic fatty liver diseases (NAFLD) is manifested in the absent of alcohol abuse. This disease is the major cause of liver failure and death among adults and children worldwide, including South Africa. Its increasing prevalence urges the need of therapeutic intervention. The main objectives of this study were to investigate the following: (1) The effect of 38.9% high fat diet (HFD)‐induced insulin resistance and fatty liver in male Wistar rats, (2) The efficacy of aqueous extracts from Sutherlandia frutescens leaves and Prunus africana bark and metformin in the treatment of HFDinduced insulin resistance and fatty liver. Male Wistar rats were fed on HFD (the HF group) or normal rat chow (the LF group) for 12 weeks. Even though the HFD‐fed rats had developed insulin resistance by week 12, fatty liver developed by week 16. After week 12, the HF group was divided into four groups of 6‐7 rats each and three of those groups were gavaged with either 0.125 mg P. africana extract/kg bwt/day (the HF+Pa group) or 50 mg S. frutescens extract kg bwt/day (the HF+Sf group) or 16 mg metformin/ kg bwt/day (HF+Met group), while kept on the same diet for an additional of 4 weeks, to investigate whether two medicinal plant extracts and metformin can prevent HFD to induce fatty liver or not. After 16 weeks, the liver histological images revealed that the HF group developed fatty liver in the form of both microsteatosis and macrosteatosis. Fatty liver was confirmed by significant increased liver total lipid (TL) and activities of glucose‐6‐phosphate dehydrogenase (cG6PD) and xanthine oxidase (XO), mitochondrial NADH oxidase (mNOX) and by a decrease (P<0.05) in the activities of the homogenate superoxide dismutase (hSOD) and mitochondrial complex II in the HF group, when compared to the LF group. Since the activities of mCS and cACL enzymes were not changed in the HF group, hence increased cG6PD activity in the HF group indicates that there was increased NADPH demand for lipid accumulation from activated NEFAs taken up by the liver from circulation and for maintenance of the NADPH‐dependent antioxidants and oxidants, respectively. The obtained data also show that mitochondria of the HFD‐fed rats adapted to an increase in energy availability, thereby compensation through decreasing complex II activity, to allow electron flux from β‐oxidation to respiratory chain in the HF group. Liver TL content was significantly decreased in the rats treated with metformin and P. africana extract, but not in the rats treated with S. frutescens when compared to the HF group (P < 0.05). However, the TL content remained >5% per liver weight in all treated groups. The present study demonstrates that these two plant extracts and metformin have different glucogenic and lipogenic effects from that presented by HFD alone when compared to the LFD alone. In conclusion, metformin and P. africana extract can attenuate HFD‐induced fatty liver without changing the dietary habits. Hence S. frutescens extract is less effective in the prevention of HFD‐induced fatty liver. A change in the dietary habits is recommended to be considered during the use of these three remedies in the treatment of HFD‐induced insulin resistance and fatty liver. All three treatments enhanced antioxidant capacity, and may improve insulin resistance and fatty liver mediated by the present HFD through different mechanism of actions in the liver.
- Full Text:
- Date Issued: 2014
- Authors: Tshidino, Shonisani Cathphonia
- Date: 2014
- Subjects: Plant Extracts -- Therapeutic use , Medicinal plants
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/9066 , vital:26461
- Description: Non‐alcoholic fatty liver diseases (NAFLD) is manifested in the absent of alcohol abuse. This disease is the major cause of liver failure and death among adults and children worldwide, including South Africa. Its increasing prevalence urges the need of therapeutic intervention. The main objectives of this study were to investigate the following: (1) The effect of 38.9% high fat diet (HFD)‐induced insulin resistance and fatty liver in male Wistar rats, (2) The efficacy of aqueous extracts from Sutherlandia frutescens leaves and Prunus africana bark and metformin in the treatment of HFDinduced insulin resistance and fatty liver. Male Wistar rats were fed on HFD (the HF group) or normal rat chow (the LF group) for 12 weeks. Even though the HFD‐fed rats had developed insulin resistance by week 12, fatty liver developed by week 16. After week 12, the HF group was divided into four groups of 6‐7 rats each and three of those groups were gavaged with either 0.125 mg P. africana extract/kg bwt/day (the HF+Pa group) or 50 mg S. frutescens extract kg bwt/day (the HF+Sf group) or 16 mg metformin/ kg bwt/day (HF+Met group), while kept on the same diet for an additional of 4 weeks, to investigate whether two medicinal plant extracts and metformin can prevent HFD to induce fatty liver or not. After 16 weeks, the liver histological images revealed that the HF group developed fatty liver in the form of both microsteatosis and macrosteatosis. Fatty liver was confirmed by significant increased liver total lipid (TL) and activities of glucose‐6‐phosphate dehydrogenase (cG6PD) and xanthine oxidase (XO), mitochondrial NADH oxidase (mNOX) and by a decrease (P<0.05) in the activities of the homogenate superoxide dismutase (hSOD) and mitochondrial complex II in the HF group, when compared to the LF group. Since the activities of mCS and cACL enzymes were not changed in the HF group, hence increased cG6PD activity in the HF group indicates that there was increased NADPH demand for lipid accumulation from activated NEFAs taken up by the liver from circulation and for maintenance of the NADPH‐dependent antioxidants and oxidants, respectively. The obtained data also show that mitochondria of the HFD‐fed rats adapted to an increase in energy availability, thereby compensation through decreasing complex II activity, to allow electron flux from β‐oxidation to respiratory chain in the HF group. Liver TL content was significantly decreased in the rats treated with metformin and P. africana extract, but not in the rats treated with S. frutescens when compared to the HF group (P < 0.05). However, the TL content remained >5% per liver weight in all treated groups. The present study demonstrates that these two plant extracts and metformin have different glucogenic and lipogenic effects from that presented by HFD alone when compared to the LFD alone. In conclusion, metformin and P. africana extract can attenuate HFD‐induced fatty liver without changing the dietary habits. Hence S. frutescens extract is less effective in the prevention of HFD‐induced fatty liver. A change in the dietary habits is recommended to be considered during the use of these three remedies in the treatment of HFD‐induced insulin resistance and fatty liver. All three treatments enhanced antioxidant capacity, and may improve insulin resistance and fatty liver mediated by the present HFD through different mechanism of actions in the liver.
- Full Text:
- Date Issued: 2014
Electrical conductivity experiments on carbon-rich Karoo shales and forward modelling of aeromagnetic data across the Beattie Anomaly
- Authors: Branch, Thomas Cameron
- Date: 2014
- Subjects: Earth sciences -- South Africa -- Karoo , Geology -- South Africa -- Karoo
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10662 , http://hdl.handle.net/10948/d1014544
- Description: The Beattie Magnetic Anomaly is the world’s longest terrestrial magnetic anomaly with a strike length of over 1000 km and a wavelength in excess of 100 km. Collinear with this is a large belt of elevated crustal conductivities called the Southern Cape Conductive Belt. Historical crustal interpretations proposed a common source of serpentinized ophiolite as an explanation for both the anomalous crustal magnetic susceptibility and electrical conductivities. Spreading between the Western and Eastern Cape of South Africa the mid- to lower crust that hosts these anomalies is obscured by the overlying Cape and Karoo Supergroups. Between 2003 and 2006, three high resolution geophysical experiments were completed across the surface maximum of the Beattie Magnetic Anomaly (BMA) and the Southern Cape Conductive Belt (SCCB). These included a magnetotelluric (MT) survey and near vertical reflection and wide angle refraction seismic profiles. Within the MT inversion model the SCCB appeared as a composite anomaly, which included a mid-crustal conductor which is spatially associated with the BMA and a laterally continuous upper crustal conductor which is located at depths equivalent to the lower Karoo Supergroup. Subsequently; the upper crustal conductor was identified in northern and eastern extensions of the magnetotelluric profile; a distance in excess of 400 km. Historical magnetometer and Schlumberger Sounding experiments have previously identified elevated conductivities in the Karoo sequences which were attributed to the Whitehill and Prince Albert formations. These carboniferous, transgressive sediments are known to be conductive from borehole conductivity surveys and direct measurements at surface. In order to constrain the conductive properties of these sediments, impedance spectroscopy (IS) experiments were completed on core samples collected from a historical borehole drilled near to the MT profile. Part One of this thesis presents the results of these experiments, which support the proposition that the Whitehill and Prince Albert Formations are responsible for the laterally continuous, sub-horizontal, upper crustal conductor visible in the MT inversion model. Vitrinite reflectance studies were performed on the same samples by the Montanuniversität, in Leoben, these results corroborate the proposition that elevated organic carbon, of meta-anthracite rank, is the primary conductive phase for the Whitehill and Prince Albert formations. Part two of this thesis completed forward modelling exercises using historical aeromagnetic data previously collected across the Beattie Magnetic Anomaly. Preliminary models were unable to fit the geometry of any single magnetic model with conductors present in the MT inversion model discounting the proposition that the SCCB and BMA arise from a single crustal unit. Two constrained models were arrived at through an iterative process that sought a best fit between the measured data and the NVR crustal interpretations. The first model, proposes a largely resistive unit which incorporates portions of elevated crustal conductivity; these conductors are spatially correlated to crustal portions also characterised by high seismic reflectivity. The size of this modelled body suggest the likely host of the BMA is an intermediate plutonic terrane, analogous with the Natal sector of the Namaqua Natal Mobile Belt as well as the Heimefrontfjella in Dronning Maud Land, Antarctica, with magnetite hosted within shear zones. This is in agreement with previous studies. The second model proposes a lower crustal sliver imaged in the NVR data at depths proximal to the Curie Isotherm for magnetite and hematite as the source of the BMA. At these depths geomagnetic properties such as burial magnetisation or thermo-viscous remanent magnetism (TVRM) can potentially be linked to regional scale tectonic processes and can theoretically elevate a body’s net magnetic susceptibility. TVRM has been proposed for long wavelength crustal anomalies elsewhere.
- Full Text:
- Date Issued: 2014
- Authors: Branch, Thomas Cameron
- Date: 2014
- Subjects: Earth sciences -- South Africa -- Karoo , Geology -- South Africa -- Karoo
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10662 , http://hdl.handle.net/10948/d1014544
- Description: The Beattie Magnetic Anomaly is the world’s longest terrestrial magnetic anomaly with a strike length of over 1000 km and a wavelength in excess of 100 km. Collinear with this is a large belt of elevated crustal conductivities called the Southern Cape Conductive Belt. Historical crustal interpretations proposed a common source of serpentinized ophiolite as an explanation for both the anomalous crustal magnetic susceptibility and electrical conductivities. Spreading between the Western and Eastern Cape of South Africa the mid- to lower crust that hosts these anomalies is obscured by the overlying Cape and Karoo Supergroups. Between 2003 and 2006, three high resolution geophysical experiments were completed across the surface maximum of the Beattie Magnetic Anomaly (BMA) and the Southern Cape Conductive Belt (SCCB). These included a magnetotelluric (MT) survey and near vertical reflection and wide angle refraction seismic profiles. Within the MT inversion model the SCCB appeared as a composite anomaly, which included a mid-crustal conductor which is spatially associated with the BMA and a laterally continuous upper crustal conductor which is located at depths equivalent to the lower Karoo Supergroup. Subsequently; the upper crustal conductor was identified in northern and eastern extensions of the magnetotelluric profile; a distance in excess of 400 km. Historical magnetometer and Schlumberger Sounding experiments have previously identified elevated conductivities in the Karoo sequences which were attributed to the Whitehill and Prince Albert formations. These carboniferous, transgressive sediments are known to be conductive from borehole conductivity surveys and direct measurements at surface. In order to constrain the conductive properties of these sediments, impedance spectroscopy (IS) experiments were completed on core samples collected from a historical borehole drilled near to the MT profile. Part One of this thesis presents the results of these experiments, which support the proposition that the Whitehill and Prince Albert Formations are responsible for the laterally continuous, sub-horizontal, upper crustal conductor visible in the MT inversion model. Vitrinite reflectance studies were performed on the same samples by the Montanuniversität, in Leoben, these results corroborate the proposition that elevated organic carbon, of meta-anthracite rank, is the primary conductive phase for the Whitehill and Prince Albert formations. Part two of this thesis completed forward modelling exercises using historical aeromagnetic data previously collected across the Beattie Magnetic Anomaly. Preliminary models were unable to fit the geometry of any single magnetic model with conductors present in the MT inversion model discounting the proposition that the SCCB and BMA arise from a single crustal unit. Two constrained models were arrived at through an iterative process that sought a best fit between the measured data and the NVR crustal interpretations. The first model, proposes a largely resistive unit which incorporates portions of elevated crustal conductivity; these conductors are spatially correlated to crustal portions also characterised by high seismic reflectivity. The size of this modelled body suggest the likely host of the BMA is an intermediate plutonic terrane, analogous with the Natal sector of the Namaqua Natal Mobile Belt as well as the Heimefrontfjella in Dronning Maud Land, Antarctica, with magnetite hosted within shear zones. This is in agreement with previous studies. The second model proposes a lower crustal sliver imaged in the NVR data at depths proximal to the Curie Isotherm for magnetite and hematite as the source of the BMA. At these depths geomagnetic properties such as burial magnetisation or thermo-viscous remanent magnetism (TVRM) can potentially be linked to regional scale tectonic processes and can theoretically elevate a body’s net magnetic susceptibility. TVRM has been proposed for long wavelength crustal anomalies elsewhere.
- Full Text:
- Date Issued: 2014
Electron microscopy characterisation of polycrystalline silicon carbide
- Authors: Ndzane, Nolufefe Muriel
- Date: 2014
- Subjects: Electron microscopy , Silicon carbide
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10553 , http://hdl.handle.net/10948/d1020634
- Description: This dissertation focuses on an electron microscopy investigation of the microstructure of SiC layers in TRISO coated particles deposited by chemical vapour deposition under different experimental conditions, which include temperature, concentration of gases and deposition time. The polycrystalline β-SiC was deposited from the decomposition of methyl trichlorosilane MTS in the presence of hydrogen (H2) as carrier gas. Scanning electron microscopy (SEM), using the backscattered electron (BSE) mode, was used to image the microstructure of and defects in the SiC layers of TRISO particles. Electron backscatter diffraction (EBSD) in the SEM was used to determine the SiC grain sizes and distribution thereof in TRISO particles deposited under different conditions. For samples with a poor EBSD indexing rate, transmission Kikuchi diffraction and transmission electron microscopy (TEM) investigations were also carried out. From the results, the effects of growth temperature on the SiC microstructure, specifically on the grain size and shape and the porosity were determined. The effects of cooling or non-cooling of the gas inlet nozzle on the SiC microstructure were also investigated. TEM and scanning TEM (STEM) analyses of the SiC layers in TRISO particles were performed to image the defects and reveal the crystallinity of SiC layers. The microstructure and composition of SiC tubes fabricated by reaction bonding (RB) was also investigated by using electron microscopy and Raman spectroscopy. SEM-BSE imaging of RBSiC samples allowed the identification of impurities and free silicon in the RBSiC. Finally, the penetration of the metallic fission product, palladium, in reaction bonded SiC at a temperature of a 1000ºC is determined. A brief comment on the suitability of RBSiC as candidate for fuel cladding in a PWR is made. A short discussion of the suitability of the characterisation techniques used is included at the end.
- Full Text:
- Date Issued: 2014
- Authors: Ndzane, Nolufefe Muriel
- Date: 2014
- Subjects: Electron microscopy , Silicon carbide
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10553 , http://hdl.handle.net/10948/d1020634
- Description: This dissertation focuses on an electron microscopy investigation of the microstructure of SiC layers in TRISO coated particles deposited by chemical vapour deposition under different experimental conditions, which include temperature, concentration of gases and deposition time. The polycrystalline β-SiC was deposited from the decomposition of methyl trichlorosilane MTS in the presence of hydrogen (H2) as carrier gas. Scanning electron microscopy (SEM), using the backscattered electron (BSE) mode, was used to image the microstructure of and defects in the SiC layers of TRISO particles. Electron backscatter diffraction (EBSD) in the SEM was used to determine the SiC grain sizes and distribution thereof in TRISO particles deposited under different conditions. For samples with a poor EBSD indexing rate, transmission Kikuchi diffraction and transmission electron microscopy (TEM) investigations were also carried out. From the results, the effects of growth temperature on the SiC microstructure, specifically on the grain size and shape and the porosity were determined. The effects of cooling or non-cooling of the gas inlet nozzle on the SiC microstructure were also investigated. TEM and scanning TEM (STEM) analyses of the SiC layers in TRISO particles were performed to image the defects and reveal the crystallinity of SiC layers. The microstructure and composition of SiC tubes fabricated by reaction bonding (RB) was also investigated by using electron microscopy and Raman spectroscopy. SEM-BSE imaging of RBSiC samples allowed the identification of impurities and free silicon in the RBSiC. Finally, the penetration of the metallic fission product, palladium, in reaction bonded SiC at a temperature of a 1000ºC is determined. A brief comment on the suitability of RBSiC as candidate for fuel cladding in a PWR is made. A short discussion of the suitability of the characterisation techniques used is included at the end.
- Full Text:
- Date Issued: 2014
Enhanced visualisation techniques to support access to personal information across multiple devices
- Authors: Beets, Simone Yvonne
- Date: 2014
- Subjects: Information visualisation , Database management , Web services , Personal information management
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10500 , http://hdl.handle.net/10948/d1021136
- Description: The increasing number of devices owned by a single user makes it increasingly difficult to access, organise and visualise personal information (PI), i.e. documents and media, across these devices. The primary method that is currently used to organise and visualise PI is the hierarchical folder structure, which is a familiar and widely used means to manage PI. However, this hierarchy does not effectively support personal information management (PIM) across multiple devices. Current solutions, such as the Personal Information Dashboard and Stuff I’ve Seen, do not support PIM across multiple devices. Alternative PIM tools, such as Dropbox and TeamViewer, attempt to provide a means of accessing PI across multiple devices, but these solutions also suffer from several limitations. The aim of this research was to investigate to what extent enhanced information visualisation (IV) techniques could be used to support accessing PI across multiple devices. An interview study was conducted to identify how PI is currently managed across multiple devices. This interview study further motivated the need for a tool to support visualising PI across multiple devices and identified requirements for such an IV tool. Several suitable IV techniques were selected and enhanced to support PIM across multiple devices. These techniques comprised an Overview using a nested circles layout, a Tag Cloud and a Partition Layout, which used a novel set-based technique. A prototype, called MyPSI, was designed and implemented incorporating these enhanced IV techniques. The requirements and design of the MyPSI prototype were validated using a conceptual walkthrough. The design of the MyPSI prototype was initially implemented for a desktop or laptop device with mouse-based interaction. A sample personal space of information (PSI) was used to evaluate the prototype in a controlled user study. The user study was used to identify any usability problems with the MyPSI prototype. The results were highly positive and the participants agreed that such a tool could be useful in future. No major problems were identified with the prototype. The MyPSI prototype was then implemented on a mobile device, specifically an Android tablet device, using a similar design, but supporting touch-based interaction. Users were allowed to upload their own PSI using Dropbox, which was visualised by the MyPSI prototype. A field study was conducted following the Multi-dimensional In-depth Long-term Case Studies approach specifically designed for IV evaluation. The field study was conducted over a two-week period, evaluating both the desktop and mobile versions of the MyPSI prototype. Both versions received positive results, but the desktop version was slightly preferred over the mobile version, mainly due to familiarity and problems experienced with the mobile implementation. Design recommendations were derived to inform future designs of IV tools to support accessing PI across multiple devices. This research has shown that IV techniques can be enhanced to effectively support accessing PI across multiple devices. Future work will involve customising the MyPSI prototype for mobile phones and supporting additional platforms.
- Full Text:
- Date Issued: 2014
- Authors: Beets, Simone Yvonne
- Date: 2014
- Subjects: Information visualisation , Database management , Web services , Personal information management
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10500 , http://hdl.handle.net/10948/d1021136
- Description: The increasing number of devices owned by a single user makes it increasingly difficult to access, organise and visualise personal information (PI), i.e. documents and media, across these devices. The primary method that is currently used to organise and visualise PI is the hierarchical folder structure, which is a familiar and widely used means to manage PI. However, this hierarchy does not effectively support personal information management (PIM) across multiple devices. Current solutions, such as the Personal Information Dashboard and Stuff I’ve Seen, do not support PIM across multiple devices. Alternative PIM tools, such as Dropbox and TeamViewer, attempt to provide a means of accessing PI across multiple devices, but these solutions also suffer from several limitations. The aim of this research was to investigate to what extent enhanced information visualisation (IV) techniques could be used to support accessing PI across multiple devices. An interview study was conducted to identify how PI is currently managed across multiple devices. This interview study further motivated the need for a tool to support visualising PI across multiple devices and identified requirements for such an IV tool. Several suitable IV techniques were selected and enhanced to support PIM across multiple devices. These techniques comprised an Overview using a nested circles layout, a Tag Cloud and a Partition Layout, which used a novel set-based technique. A prototype, called MyPSI, was designed and implemented incorporating these enhanced IV techniques. The requirements and design of the MyPSI prototype were validated using a conceptual walkthrough. The design of the MyPSI prototype was initially implemented for a desktop or laptop device with mouse-based interaction. A sample personal space of information (PSI) was used to evaluate the prototype in a controlled user study. The user study was used to identify any usability problems with the MyPSI prototype. The results were highly positive and the participants agreed that such a tool could be useful in future. No major problems were identified with the prototype. The MyPSI prototype was then implemented on a mobile device, specifically an Android tablet device, using a similar design, but supporting touch-based interaction. Users were allowed to upload their own PSI using Dropbox, which was visualised by the MyPSI prototype. A field study was conducted following the Multi-dimensional In-depth Long-term Case Studies approach specifically designed for IV evaluation. The field study was conducted over a two-week period, evaluating both the desktop and mobile versions of the MyPSI prototype. Both versions received positive results, but the desktop version was slightly preferred over the mobile version, mainly due to familiarity and problems experienced with the mobile implementation. Design recommendations were derived to inform future designs of IV tools to support accessing PI across multiple devices. This research has shown that IV techniques can be enhanced to effectively support accessing PI across multiple devices. Future work will involve customising the MyPSI prototype for mobile phones and supporting additional platforms.
- Full Text:
- Date Issued: 2014
Good's casualty for time series: a regime-switching framework
- Authors: Mlambo, Farai Fredric
- Date: 2014
- Subjects: Time-series analysis , Econometrics
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10948/6018 , vital:21025
- Description: Causal analysis is a significant role-playing field in the applied sciences such as statistics, econometrics, and technometrics. Particularly, probability-raising models have warranted significant research interest. Most of the discussions in this area are philosophical in nature. Contemporarily, the econometric causality theory, developed by C.J.W. Granger, is popular in practical, time series causal applications. While this type of causality technique has many strong features, it has serious limitations. The processes studied, in particular, should be stationary and causal relationships are restricted to be linear. However, we cannot classify regime-switching processes as linear and stationary. I.J. Good proposed a probabilistic, event-type explication of causality that circumvents some of the limitations of Granger’s methodology. This work uses the probability raising causality ideology, as postulated by Good, to propose some causal analysis methodology applicable in a stochastic, non-stationary domain. There is a proposal made for a Good’s causality test, by transforming the originally specified probabilistic causality theory from random events to a stochastic, regime-switching framework. The researcher performed methodological validation via causality simulations for a Markov, regime-switching model. The proposed test can be used to detect whether none stochastic process is causal to the observed behaviour of another, probabilistically. In particular, the regime-switch causality explication proposed herein is pivotal to the results articulated. This research also examines the power of the proposed test by using simulations, and outlines some steps that one may take in using the test in a practical setting.
- Full Text:
- Date Issued: 2014
- Authors: Mlambo, Farai Fredric
- Date: 2014
- Subjects: Time-series analysis , Econometrics
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10948/6018 , vital:21025
- Description: Causal analysis is a significant role-playing field in the applied sciences such as statistics, econometrics, and technometrics. Particularly, probability-raising models have warranted significant research interest. Most of the discussions in this area are philosophical in nature. Contemporarily, the econometric causality theory, developed by C.J.W. Granger, is popular in practical, time series causal applications. While this type of causality technique has many strong features, it has serious limitations. The processes studied, in particular, should be stationary and causal relationships are restricted to be linear. However, we cannot classify regime-switching processes as linear and stationary. I.J. Good proposed a probabilistic, event-type explication of causality that circumvents some of the limitations of Granger’s methodology. This work uses the probability raising causality ideology, as postulated by Good, to propose some causal analysis methodology applicable in a stochastic, non-stationary domain. There is a proposal made for a Good’s causality test, by transforming the originally specified probabilistic causality theory from random events to a stochastic, regime-switching framework. The researcher performed methodological validation via causality simulations for a Markov, regime-switching model. The proposed test can be used to detect whether none stochastic process is causal to the observed behaviour of another, probabilistically. In particular, the regime-switch causality explication proposed herein is pivotal to the results articulated. This research also examines the power of the proposed test by using simulations, and outlines some steps that one may take in using the test in a practical setting.
- Full Text:
- Date Issued: 2014
Identification of membrane biomakers for colorectal cancer using an in-solico and molecular approach
- Authors: Van Vuuren, Larry Peter
- Date: 2014
- Subjects: Cancer -- Research , Colon (Anatomy) -- Cancer , Rectum -- Cancer
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47970 , vital:40457
- Description: The aim of this study was to identify membrane biomarkers for colorectal cancer using an insilico and molecular approach. Colorectal cancer (CRC) globally accounts for more than half a million deaths. In South Africa alone, approximately one in 97 men is at risk of getting CRC; and for women, it is one in 162. Novel and non-invasive diagnostic tools, such as biomarkers, are needed for early CRC detection. In order to reduce the fatality rate in this disease, Biomarkers are used as indicators of a biological state; and they are measurable in biological media. They can be used to distinguish between a diseased state and a normal state, thus aiding diagnostics, response to specific therapies, and screening for an early diagnosis. A gene list of potential CRC biomarkers was generated by mining two gene databases, namely: Oncomine and Gene Expression Atlas. A total of 44 candidate genes were identified, based on their location on the cell surface, using the Database for Annotation, Visualisation and Integrated Discovery. These 44 genes were then subjected to an in-depth literature mining. The literature search parameters in PubMed, PubMed Central, Google Scholar and Science direct revealed publications showing that 23 genes were validated, while 21 genes were not validated. Nineteen genes were selected for gene validation in human colorectal cancer and healthy tissue of twelve patients. Total RNA was extracted from 12 colorectal cancer and 12 healthy tissue samples. The RNA was then quantified and reverse-transcribed into cDNA for gene expression analysis. The qPCR running conditions were optimized, by running a melting curve, in order to determine the optimum annealing temperatures. Primarily melt curves were run for nineteen of these twenty-one genes. Melt-curve analysis showed that nine genes were poor candidates for further validation studies; and therefore, only ten genes, namely: AGTRAP, ANKRD46, BACE2, CFB, CIAO1, NOMO3, PTDSS1, SLC5A6, TNFRSF12A and ZDHHC9 were validated by qPCR in human resected colorectal carcinoma and the normal tissues of twelve patients. The qPCR results showed that ZDHHC9 and the SLC5A6 genes were the only two statistically significant ones; and they were found to be down-regulated in human colorectal cancer vs healthy tissue samples.
- Full Text:
- Date Issued: 2014
Identification of membrane biomakers for colorectal cancer using an in-solico and molecular approach
- Authors: Van Vuuren, Larry Peter
- Date: 2014
- Subjects: Cancer -- Research , Colon (Anatomy) -- Cancer , Rectum -- Cancer
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47970 , vital:40457
- Description: The aim of this study was to identify membrane biomarkers for colorectal cancer using an insilico and molecular approach. Colorectal cancer (CRC) globally accounts for more than half a million deaths. In South Africa alone, approximately one in 97 men is at risk of getting CRC; and for women, it is one in 162. Novel and non-invasive diagnostic tools, such as biomarkers, are needed for early CRC detection. In order to reduce the fatality rate in this disease, Biomarkers are used as indicators of a biological state; and they are measurable in biological media. They can be used to distinguish between a diseased state and a normal state, thus aiding diagnostics, response to specific therapies, and screening for an early diagnosis. A gene list of potential CRC biomarkers was generated by mining two gene databases, namely: Oncomine and Gene Expression Atlas. A total of 44 candidate genes were identified, based on their location on the cell surface, using the Database for Annotation, Visualisation and Integrated Discovery. These 44 genes were then subjected to an in-depth literature mining. The literature search parameters in PubMed, PubMed Central, Google Scholar and Science direct revealed publications showing that 23 genes were validated, while 21 genes were not validated. Nineteen genes were selected for gene validation in human colorectal cancer and healthy tissue of twelve patients. Total RNA was extracted from 12 colorectal cancer and 12 healthy tissue samples. The RNA was then quantified and reverse-transcribed into cDNA for gene expression analysis. The qPCR running conditions were optimized, by running a melting curve, in order to determine the optimum annealing temperatures. Primarily melt curves were run for nineteen of these twenty-one genes. Melt-curve analysis showed that nine genes were poor candidates for further validation studies; and therefore, only ten genes, namely: AGTRAP, ANKRD46, BACE2, CFB, CIAO1, NOMO3, PTDSS1, SLC5A6, TNFRSF12A and ZDHHC9 were validated by qPCR in human resected colorectal carcinoma and the normal tissues of twelve patients. The qPCR results showed that ZDHHC9 and the SLC5A6 genes were the only two statistically significant ones; and they were found to be down-regulated in human colorectal cancer vs healthy tissue samples.
- Full Text:
- Date Issued: 2014
In vitro induction of cell death pathways by artemisia afra extract and isolation of an active compound, isoalantolactone
- Authors: Venables, Luanne
- Date: 2014
- Subjects: Medicinal plants -- South Africa , Cell death
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10363 , http://hdl.handle.net/10948/d1021087
- Description: Artemisia afra is one of the oldest, most well known and widely used traditional medicinal plants in South Africa. It is used to treat many different medical conditions, particularly respiratory and inflammatory ailments. There is no reported evidence of its use for the treatment of cancer but due to its reported cytotoxicity, an investigation of the mode of cell death induced by an ethanol A. afra extract using two cancer cell lines was done. IC50 values of 18.21 and 31.88 μg/mL of ethanol extracts were determined against U937 and HeLa cancer cells, respectively. An IC50 value of the aqueous extract was greater than 250 μg/mL. The ethanol extract was not cytotoxic against confluent control cell lines, Chang Liver and Vero cells. The effect of the cytotoxic ethanol A. afra extract on U937 and HeLa cells and their progression through the cell cycle, apoptosis and mitochondrial membrane potential was investigated. After 12 hours of treatment with A. afra a delay in G2/M phase of the cell cycle was evident. Apoptosis was confirmed using the TUNEL assay for DNA fragmentation, as well as fluorescent staining with annexin V-FITC. Apoptosis was evident with the positive control and A. afra treatment at 24 and 48 hours. JC-1 staining showed a decrease in mitochondrial membrane potential at 24 hours. It was deduced that A. afra ethanol extract induces caspase-dependent apoptosis in a mitochondrial dependent manner. Plants harbour many compounds that are not only useful to the plants but also to mankind. Many metabolites have been isolated from A. afra and their biological activity characterised. Due to observed apoptosis induction, isolation of cytotoxic compounds was done and a new sesquiterpene lactone from A. afra was isolated. Structural elucidation of the compound was done by IR, 1D and 2D NMR, CD and mass spectrometry and it was identified as isoalantolactone. HeLa cancer cells were treated with isoalantolactone and cytotoxicity was exhibited in a dose-dependent manner. A low IC50 value of 8.15 ± 1.16 μM was achieved. This study showed that isoalantolactone is partly responsible for the observed A. afra cytotoxicity. Due to the evidence of G2/M arrest, the anti-mitotic potential and the possible onset of mitotic catastrophe by A. afra and isoalantolactone was investigated. It was evident from various flow cytometric analysis of cyclin B1 and phospho-H3 and confocal microscopy that A. afra does possess anti-mitotic activity by causing hyperpolymerisation of tubulin and cells progress into the mitotic phase where M arrest is experienced. The anti-inflammatory activity of sesquiterpene lactones is well documented; however, the anti-inflammatory activity of A. afra is not. Here, it is reported that the production of NO and COX-2 protein levels in RAW 264.7 cells decrease in the presence of A. afra and isoalantolactone after stimulation with LPS. The activated NF-κB subunit, p65 was also investigated. The results suggest that A. afra and isoalantolactone inhibit p65 activation as a decrease in the activated subunit was evident. Thus, the results indicate that exposure to A. afra and isoalantolactone induces an anti-inflammatory response. In conclusion, this study shows, for the first time, the mechanism of induced apoptosis, the anti-mitotic and anti-inflammatory activity of A. afra and its isolated compound, isoalantolactone. It also proves that although extensive research may have been done on a particular plant, as with A. afra, more can be discovered leading to the identification of new compounds and integration of signalling pathways that can be exploited for the treatment of various diseases and ailments.
- Full Text:
- Date Issued: 2014
- Authors: Venables, Luanne
- Date: 2014
- Subjects: Medicinal plants -- South Africa , Cell death
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10363 , http://hdl.handle.net/10948/d1021087
- Description: Artemisia afra is one of the oldest, most well known and widely used traditional medicinal plants in South Africa. It is used to treat many different medical conditions, particularly respiratory and inflammatory ailments. There is no reported evidence of its use for the treatment of cancer but due to its reported cytotoxicity, an investigation of the mode of cell death induced by an ethanol A. afra extract using two cancer cell lines was done. IC50 values of 18.21 and 31.88 μg/mL of ethanol extracts were determined against U937 and HeLa cancer cells, respectively. An IC50 value of the aqueous extract was greater than 250 μg/mL. The ethanol extract was not cytotoxic against confluent control cell lines, Chang Liver and Vero cells. The effect of the cytotoxic ethanol A. afra extract on U937 and HeLa cells and their progression through the cell cycle, apoptosis and mitochondrial membrane potential was investigated. After 12 hours of treatment with A. afra a delay in G2/M phase of the cell cycle was evident. Apoptosis was confirmed using the TUNEL assay for DNA fragmentation, as well as fluorescent staining with annexin V-FITC. Apoptosis was evident with the positive control and A. afra treatment at 24 and 48 hours. JC-1 staining showed a decrease in mitochondrial membrane potential at 24 hours. It was deduced that A. afra ethanol extract induces caspase-dependent apoptosis in a mitochondrial dependent manner. Plants harbour many compounds that are not only useful to the plants but also to mankind. Many metabolites have been isolated from A. afra and their biological activity characterised. Due to observed apoptosis induction, isolation of cytotoxic compounds was done and a new sesquiterpene lactone from A. afra was isolated. Structural elucidation of the compound was done by IR, 1D and 2D NMR, CD and mass spectrometry and it was identified as isoalantolactone. HeLa cancer cells were treated with isoalantolactone and cytotoxicity was exhibited in a dose-dependent manner. A low IC50 value of 8.15 ± 1.16 μM was achieved. This study showed that isoalantolactone is partly responsible for the observed A. afra cytotoxicity. Due to the evidence of G2/M arrest, the anti-mitotic potential and the possible onset of mitotic catastrophe by A. afra and isoalantolactone was investigated. It was evident from various flow cytometric analysis of cyclin B1 and phospho-H3 and confocal microscopy that A. afra does possess anti-mitotic activity by causing hyperpolymerisation of tubulin and cells progress into the mitotic phase where M arrest is experienced. The anti-inflammatory activity of sesquiterpene lactones is well documented; however, the anti-inflammatory activity of A. afra is not. Here, it is reported that the production of NO and COX-2 protein levels in RAW 264.7 cells decrease in the presence of A. afra and isoalantolactone after stimulation with LPS. The activated NF-κB subunit, p65 was also investigated. The results suggest that A. afra and isoalantolactone inhibit p65 activation as a decrease in the activated subunit was evident. Thus, the results indicate that exposure to A. afra and isoalantolactone induces an anti-inflammatory response. In conclusion, this study shows, for the first time, the mechanism of induced apoptosis, the anti-mitotic and anti-inflammatory activity of A. afra and its isolated compound, isoalantolactone. It also proves that although extensive research may have been done on a particular plant, as with A. afra, more can be discovered leading to the identification of new compounds and integration of signalling pathways that can be exploited for the treatment of various diseases and ailments.
- Full Text:
- Date Issued: 2014
Indigenous knowledge and climate change : insights from Muzarabani, Zimbabwe
- Authors: Chanza, Nelson
- Date: 2014
- Subjects: Indigenous peoples – Ecology – Zimbabwe -- Centenary District , Climatic changes -- Social aspects – Zimbabwe -- Centenary District , Climatic changes – Zimbabwe -- Centenary District
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10671 , http://hdl.handle.net/10948/d1020299
- Description: Discourse characterising climate change has largely revolved around aspects within the realm of impact identification, mitigation and adaptation. Apparently, a burgeoning appetite to examine the role of indigenous knowledge (IK) now confronts the fronts of climate science, policy and practice. The surge in attention to localbased knowledge is attributed to growing challenges posed by change and variability in the climate system. This study argues that indigenous-based knowledge is capable of filling knowledge gaps and validating current understanding about climate change particularly at local levels. Essentially, the paucity of knowledge about local climatic events can be circumvented by engaging indigenous ‘scientists’ whose many years of direct contact with the environment have equipped them with the indispensable knowledge, skills and experiences to understand the same. Primarily, the thesis’ objectives were threefold. One, it captured useful indicators of climate change and variability from the understanding of the indigenous people, which can also be used to enhance understanding of climate change impacts.Two, it drew from the knowledge, experiences, skills and practices of the locals in order to inform appropriate community level mitigation and adaptation interventions. And, three, it highlighted the fact that knowledge of the indigenous people can be used to direct research on climate change. The study area (Muzarabani in Zimbabwe) experiences recurrent droughts and floods and its villagers rely predominantly on climate-sensitive livelihoods. As such, it was selected to provide a reliable case on IK practices and experiences of the people witnessing climatic events. The study was framed within an epistemological and methodological configuration of emancipatory pedagogy that looks at the generators of climate knowledge as ‘scientists’ in their own right. A qualitative elicitation interviewing technique involving in-depth discussions with traditional leaders and elderly knowledgeable citizens was conducted. The participants were selected through chain referrals until the level of theoretical saturation. In addition, directed field observations, document analysis and key informant interviews with other respondents selected through theoretical sampling enhanced the robustness of data acquisition methods. Group-based participatory data analysis and reflexive pragmatism also enhanced rigour and quality of research findings intended to balance between the strictures of the scientific audience and the views of the knowledge generators. Three key themes were derived from IK-climate change linkages as: indigenous based indicators of climate change, indigenous-based mitigation and indigenous based adaptation. A range of indigenous-based indicators identified pointed to a progressively drier climate with shorter growing seasons that are also punctuated by mid-season dry spells. A trend towards increased desiccation of water bodies (rivers, ponds and vleis) was further observed. There is also an upsurge in the abundance and pestiferous nature of Macrotermes spp, Quelea quelea and Acanthoplus discoidalis, which are most likely related to climate change. Some of these indicators closely match with those used in mainstream climate science and they also serve to understand climate change impacts at a finer local level of analysis. Indigenous-based mitigation is mainly driven by the notion of sacredness where the locals regard forestry, certain trees and vleis as sacrosanct. Tampering with these is believed to upset the spirits who have powers to influence climate. Opportunities associated with IK deployment in climate mitigation are understood from the viewpoint of enhancing greenhouse gas (GHG) sinks and that of reducing vulnerability to extreme climatic events. Specifically, this can be achieved through enhancing GHG sequestration through forestry and land-use management initiatives; that is, reducing emissions from deforestation and forestry related degradation (REDD+) and Land Use and Land-Use Cover and Forestry (LULUCF). These two are the dominant schemes adopted by the Intergovernmental Panel on Climate Change (IPCC) to govern climate mitigation. Indigenous disaster risk management (DRM) strategies abound in drought, famine, flood and violent storms through various forms such as Zunde raMambo, nhimbe, rain-making ceremonies and community early warning systems (EWS).The locals in Muzarabani are not passive observers of the changing climate system. Increasing environmental risks necessitates them to devise countermeasures for responding to climatic stimuli with the intention of minimising harm and/or enhancing the benefits brought about by the same. Thus, a portfolio of IK-based adaptation strategies best described as an assortment of short-term coping practices and longterm adaptive strategies were identified. These range from exploitation of ecosystem services, agricultural based interventions, riverine farming, traditional phonological knowledge (TPK) to migration. Therefore, it was revealed that community-based adaptation (CBA) can adequately leverage on IK to improve adaptive capacity and build community resilience against climate change. Clearly, the complementary role of indigenous-based knowledge cannot be disputed, given the demonstrated range of applications from identifying several indicators of change and variability in the climate system, examination of climate change impacts, to identification and assessment of mitigation and adaptation options. The study advises that exogenous climate interventions need to be congruent with indigenous based strategies to avoid maladaptation. To the climate research community therefore, it should be realised that IK is useful both as leads and as baseline knowledge for future work on the impacts of climate change, and in the assessment of climate interventions. In this regard, the remaining challenge is to formulate a framework of constructive dialogue between indigenous scientists and conventional scientists so as to make sure that the mutual benefits of the two knowledge forms are adequately harnessed. Handled well, such collaborative effort would ensure enhanced climate change knowledge for successful mitigation and adaptation strategies. Handled poorly, there is a risk that the developmental needs of communities exposed to climatic events would not be addressed.
- Full Text:
- Date Issued: 2014
- Authors: Chanza, Nelson
- Date: 2014
- Subjects: Indigenous peoples – Ecology – Zimbabwe -- Centenary District , Climatic changes -- Social aspects – Zimbabwe -- Centenary District , Climatic changes – Zimbabwe -- Centenary District
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10671 , http://hdl.handle.net/10948/d1020299
- Description: Discourse characterising climate change has largely revolved around aspects within the realm of impact identification, mitigation and adaptation. Apparently, a burgeoning appetite to examine the role of indigenous knowledge (IK) now confronts the fronts of climate science, policy and practice. The surge in attention to localbased knowledge is attributed to growing challenges posed by change and variability in the climate system. This study argues that indigenous-based knowledge is capable of filling knowledge gaps and validating current understanding about climate change particularly at local levels. Essentially, the paucity of knowledge about local climatic events can be circumvented by engaging indigenous ‘scientists’ whose many years of direct contact with the environment have equipped them with the indispensable knowledge, skills and experiences to understand the same. Primarily, the thesis’ objectives were threefold. One, it captured useful indicators of climate change and variability from the understanding of the indigenous people, which can also be used to enhance understanding of climate change impacts.Two, it drew from the knowledge, experiences, skills and practices of the locals in order to inform appropriate community level mitigation and adaptation interventions. And, three, it highlighted the fact that knowledge of the indigenous people can be used to direct research on climate change. The study area (Muzarabani in Zimbabwe) experiences recurrent droughts and floods and its villagers rely predominantly on climate-sensitive livelihoods. As such, it was selected to provide a reliable case on IK practices and experiences of the people witnessing climatic events. The study was framed within an epistemological and methodological configuration of emancipatory pedagogy that looks at the generators of climate knowledge as ‘scientists’ in their own right. A qualitative elicitation interviewing technique involving in-depth discussions with traditional leaders and elderly knowledgeable citizens was conducted. The participants were selected through chain referrals until the level of theoretical saturation. In addition, directed field observations, document analysis and key informant interviews with other respondents selected through theoretical sampling enhanced the robustness of data acquisition methods. Group-based participatory data analysis and reflexive pragmatism also enhanced rigour and quality of research findings intended to balance between the strictures of the scientific audience and the views of the knowledge generators. Three key themes were derived from IK-climate change linkages as: indigenous based indicators of climate change, indigenous-based mitigation and indigenous based adaptation. A range of indigenous-based indicators identified pointed to a progressively drier climate with shorter growing seasons that are also punctuated by mid-season dry spells. A trend towards increased desiccation of water bodies (rivers, ponds and vleis) was further observed. There is also an upsurge in the abundance and pestiferous nature of Macrotermes spp, Quelea quelea and Acanthoplus discoidalis, which are most likely related to climate change. Some of these indicators closely match with those used in mainstream climate science and they also serve to understand climate change impacts at a finer local level of analysis. Indigenous-based mitigation is mainly driven by the notion of sacredness where the locals regard forestry, certain trees and vleis as sacrosanct. Tampering with these is believed to upset the spirits who have powers to influence climate. Opportunities associated with IK deployment in climate mitigation are understood from the viewpoint of enhancing greenhouse gas (GHG) sinks and that of reducing vulnerability to extreme climatic events. Specifically, this can be achieved through enhancing GHG sequestration through forestry and land-use management initiatives; that is, reducing emissions from deforestation and forestry related degradation (REDD+) and Land Use and Land-Use Cover and Forestry (LULUCF). These two are the dominant schemes adopted by the Intergovernmental Panel on Climate Change (IPCC) to govern climate mitigation. Indigenous disaster risk management (DRM) strategies abound in drought, famine, flood and violent storms through various forms such as Zunde raMambo, nhimbe, rain-making ceremonies and community early warning systems (EWS).The locals in Muzarabani are not passive observers of the changing climate system. Increasing environmental risks necessitates them to devise countermeasures for responding to climatic stimuli with the intention of minimising harm and/or enhancing the benefits brought about by the same. Thus, a portfolio of IK-based adaptation strategies best described as an assortment of short-term coping practices and longterm adaptive strategies were identified. These range from exploitation of ecosystem services, agricultural based interventions, riverine farming, traditional phonological knowledge (TPK) to migration. Therefore, it was revealed that community-based adaptation (CBA) can adequately leverage on IK to improve adaptive capacity and build community resilience against climate change. Clearly, the complementary role of indigenous-based knowledge cannot be disputed, given the demonstrated range of applications from identifying several indicators of change and variability in the climate system, examination of climate change impacts, to identification and assessment of mitigation and adaptation options. The study advises that exogenous climate interventions need to be congruent with indigenous based strategies to avoid maladaptation. To the climate research community therefore, it should be realised that IK is useful both as leads and as baseline knowledge for future work on the impacts of climate change, and in the assessment of climate interventions. In this regard, the remaining challenge is to formulate a framework of constructive dialogue between indigenous scientists and conventional scientists so as to make sure that the mutual benefits of the two knowledge forms are adequately harnessed. Handled well, such collaborative effort would ensure enhanced climate change knowledge for successful mitigation and adaptation strategies. Handled poorly, there is a risk that the developmental needs of communities exposed to climatic events would not be addressed.
- Full Text:
- Date Issued: 2014
Influence of anthropogenic stressors on the behaviour and mortality of the endangered African penguin
- Authors: Nyengera, Reason
- Date: 2014
- Subjects: African penguin -- South Africa -- Algoa Bay , Birds -- Mortality -- South Africa -- Algoa Bay , Endangered species -- Breeding -- South Africa -- Algoa Bay
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3064 , vital:20395
- Description: This study investigated the potential impacts of several anthropogenic stressors on the movement and survival of African penguins in Algoa Bay, taking into account prey availability and environmental conditions (sea surface temperature and chlorophyll productivity). The primary drive for the study was based on the seismic exploration, which took place in the habitat of the endangered African penguin. The research was also carried out to understand how pelagic fishing and prey availability influence the broader behavioural and mortality aspects of penguins. To achieve this goal, I used monthly beach surveys to assess seabird mortality, admissions of penguins in rehabilitation centres and the monitoring of breeding penguins’ movement at sea through individual GPS tracking. In addition, prey distribution and abundance were monitored with acoustic surveys to assess potential changes in relation anthropogenic stressors. Breeding African penguins did not react dramatically to seismic activities, except on St Croix Island where they changed their foraging direction during the seismic period. There was no evidence of a siginficant increase in African penguin carcasses encountered or strandings along the beaches during the period of seismic activity. However, a sharp increase in encounter rate was recorded soon after seismic operations, which may potentially indicate a delay between the effect of seismic activities on penguin mortality and the encounter of the related carcasses after the operation. However, the impact of seismic surveys on penguins may be long-term rather than short term, and additional studies would be needed to reveal long-term effects of seismic activities, if any. Foraging effort of breeding African penguins increased substantially in the presence of commercial fishing activities within close proximity to the colonies. To a greater extent, at-sea movement patterns and counts of beach cast carcasses were largely influenced by prey availability. Penguins spent more time at sea, traveled longer and covered a larger foraging area during periods of relatvely low pelagic fish abundance. There was also a sharp increase in African penguin mortality during periods of low prey availability in the Bay. However, environmental conditions showed some influence over these interactions. Foraging effort of breeding African penguins increased substantially in the presence of commercial fishing activities within close proximity to the colonies. To a greater extent, at-sea movement patterns and counts of beach cast carcasses were largely influenced by prey availability. Penguins spent more time at sea, traveled longer and covered a larger foraging area during periods of relatvely low pelagic fish abundance. There was also a sharp increase in African penguin mortality during periods of low prey availability in the Bay. However, environmental conditions showed some influence over these interactions. For example a red tide event during in period of low prey availability, made it difficult to understand impacts of prey on penguins difficult. Both anthropogenic stressors and environmental conditions influenced African penguins’ behaviour and survival. Due to the worrying trend of African penguins in South Africa for the past few years, all conservation management efforts to increase penguin numbers and limit their mortality are necessary. This study highlights the negative impact of industrial fishing on this Endangered species and the rapid increase in mortality of penguins during times of low prey availability. A network of Marine Protected Areas would certainly increase food availability to African penguins by limiting competition with fisheries, and contribute to increasing the population numbers.
- Full Text:
- Date Issued: 2014
- Authors: Nyengera, Reason
- Date: 2014
- Subjects: African penguin -- South Africa -- Algoa Bay , Birds -- Mortality -- South Africa -- Algoa Bay , Endangered species -- Breeding -- South Africa -- Algoa Bay
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3064 , vital:20395
- Description: This study investigated the potential impacts of several anthropogenic stressors on the movement and survival of African penguins in Algoa Bay, taking into account prey availability and environmental conditions (sea surface temperature and chlorophyll productivity). The primary drive for the study was based on the seismic exploration, which took place in the habitat of the endangered African penguin. The research was also carried out to understand how pelagic fishing and prey availability influence the broader behavioural and mortality aspects of penguins. To achieve this goal, I used monthly beach surveys to assess seabird mortality, admissions of penguins in rehabilitation centres and the monitoring of breeding penguins’ movement at sea through individual GPS tracking. In addition, prey distribution and abundance were monitored with acoustic surveys to assess potential changes in relation anthropogenic stressors. Breeding African penguins did not react dramatically to seismic activities, except on St Croix Island where they changed their foraging direction during the seismic period. There was no evidence of a siginficant increase in African penguin carcasses encountered or strandings along the beaches during the period of seismic activity. However, a sharp increase in encounter rate was recorded soon after seismic operations, which may potentially indicate a delay between the effect of seismic activities on penguin mortality and the encounter of the related carcasses after the operation. However, the impact of seismic surveys on penguins may be long-term rather than short term, and additional studies would be needed to reveal long-term effects of seismic activities, if any. Foraging effort of breeding African penguins increased substantially in the presence of commercial fishing activities within close proximity to the colonies. To a greater extent, at-sea movement patterns and counts of beach cast carcasses were largely influenced by prey availability. Penguins spent more time at sea, traveled longer and covered a larger foraging area during periods of relatvely low pelagic fish abundance. There was also a sharp increase in African penguin mortality during periods of low prey availability in the Bay. However, environmental conditions showed some influence over these interactions. Foraging effort of breeding African penguins increased substantially in the presence of commercial fishing activities within close proximity to the colonies. To a greater extent, at-sea movement patterns and counts of beach cast carcasses were largely influenced by prey availability. Penguins spent more time at sea, traveled longer and covered a larger foraging area during periods of relatvely low pelagic fish abundance. There was also a sharp increase in African penguin mortality during periods of low prey availability in the Bay. However, environmental conditions showed some influence over these interactions. For example a red tide event during in period of low prey availability, made it difficult to understand impacts of prey on penguins difficult. Both anthropogenic stressors and environmental conditions influenced African penguins’ behaviour and survival. Due to the worrying trend of African penguins in South Africa for the past few years, all conservation management efforts to increase penguin numbers and limit their mortality are necessary. This study highlights the negative impact of industrial fishing on this Endangered species and the rapid increase in mortality of penguins during times of low prey availability. A network of Marine Protected Areas would certainly increase food availability to African penguins by limiting competition with fisheries, and contribute to increasing the population numbers.
- Full Text:
- Date Issued: 2014
Isolation, purification and partial characterisation of cancer procoagulant from placental amnion-chorion membranes and its role in angiogenesis inflammation and metastasis
- Authors: Krause, Jason
- Date: 2014
- Subjects: Coagulation , Amnion , Chorion , Metastasis , Inflammation , Neovascularization
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10350 , http://hdl.handle.net/10948/d1020897
- Description: Cancer procoagulant (EC 3.4.22.26) is an enzyme that is derived from tumour and foetal tissue, but not normal tissue. It is a direct activator of factor X and has been isolated from amnion-chorion membranes as well as from extracts and cells from human melanoma. The presence of cancer procoagulant has been associated with the malignant phenotype, as well as having a particularly high activity in metastatic cells. Cancer procoagulant activity is elevated in the serum of early stage breast cancer patients and decreased to normal in the advanced stages of the disease. In this study, cancer procoagulant was successfully isolated from amnion-chorion membranes and purified to homogeneity. The molecular weight of cancer procoagulant was determined using SDS-PAGE and was found to be 68 kDa. Cancer procoagulant was delipidated and it was shown that its activity was increased by the presence of lipids in a dose-dependent manner. Recovery of cancer procoagulant after delipidation is poor, consequently, a larger mass of sample is required to obtain sufficient amounts of delipidated material for N-terminal amino acid analysis. The optimum pH of cancer procoagulant was determined to be pH 8 and its optimal temperature was found to be 50°C. Novel synthetic substrates were designed to assay for cancer procoagulant activity. Currently, 2 potential candidates have been identified, namely, PQVR-AMC and AVSQSKP-AMC. Cancer procoagulant-induced expression of cytokines is differently modulated in the less aggressive MCF-7 cell line as compared to the metastatic and more aggressive MDA-MB-231 cell line. There are marked similarities in the inflammatory response produced by cancer procoagulant in hTERT-HDLEC and MDA-MB-231 cells, which are both associated with migratory capacity. Furthermore, cancer procoagulant-induced PDGF-β expression in hTERT-HDLEC and MDA-MB-231 cells could point to involvement of cancer procoagulant in wound healing and metastatic spread, respectively. Cancer procoagulant induced the motility of MDA-MB-231, MCF-7 and hTERT- cells in vitro in a time- and dose-dependent manner. Together, these results suggest that cancer procoagulant plays a role in the migration of breast cancer cells as well as the migration of endothelial cells.
- Full Text:
- Date Issued: 2014
- Authors: Krause, Jason
- Date: 2014
- Subjects: Coagulation , Amnion , Chorion , Metastasis , Inflammation , Neovascularization
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10350 , http://hdl.handle.net/10948/d1020897
- Description: Cancer procoagulant (EC 3.4.22.26) is an enzyme that is derived from tumour and foetal tissue, but not normal tissue. It is a direct activator of factor X and has been isolated from amnion-chorion membranes as well as from extracts and cells from human melanoma. The presence of cancer procoagulant has been associated with the malignant phenotype, as well as having a particularly high activity in metastatic cells. Cancer procoagulant activity is elevated in the serum of early stage breast cancer patients and decreased to normal in the advanced stages of the disease. In this study, cancer procoagulant was successfully isolated from amnion-chorion membranes and purified to homogeneity. The molecular weight of cancer procoagulant was determined using SDS-PAGE and was found to be 68 kDa. Cancer procoagulant was delipidated and it was shown that its activity was increased by the presence of lipids in a dose-dependent manner. Recovery of cancer procoagulant after delipidation is poor, consequently, a larger mass of sample is required to obtain sufficient amounts of delipidated material for N-terminal amino acid analysis. The optimum pH of cancer procoagulant was determined to be pH 8 and its optimal temperature was found to be 50°C. Novel synthetic substrates were designed to assay for cancer procoagulant activity. Currently, 2 potential candidates have been identified, namely, PQVR-AMC and AVSQSKP-AMC. Cancer procoagulant-induced expression of cytokines is differently modulated in the less aggressive MCF-7 cell line as compared to the metastatic and more aggressive MDA-MB-231 cell line. There are marked similarities in the inflammatory response produced by cancer procoagulant in hTERT-HDLEC and MDA-MB-231 cells, which are both associated with migratory capacity. Furthermore, cancer procoagulant-induced PDGF-β expression in hTERT-HDLEC and MDA-MB-231 cells could point to involvement of cancer procoagulant in wound healing and metastatic spread, respectively. Cancer procoagulant induced the motility of MDA-MB-231, MCF-7 and hTERT- cells in vitro in a time- and dose-dependent manner. Together, these results suggest that cancer procoagulant plays a role in the migration of breast cancer cells as well as the migration of endothelial cells.
- Full Text:
- Date Issued: 2014
Lesson for spatial planning: post-1994 human settlement development in Nelson Mandela Bay Municipality
- Authors: Nagar, Manesh
- Date: 2014
- Subjects: Land settlement -- South Africa -- Port Elizabeth -- 21st century Human geography -- South Africa -- Port Elizabeth -- 21st century , City planning -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47992 , vital:40461
- Description: Spatial planning of human settlements in South African cities, particularly during the apartheid era, has been extensively investigated. Urban development in Nelson Mandela Bay (formerly known as Port Elizabeth) resembled most other South African cities and towns based on the informants of the apartheid spatial planning policies since 1948. Consequent to the colonial style urban forms, the typical South African city and town (including Nelson Mandela Bay) faces numerous challenges to eradicate the effects of the apartheid legacies of functional and structural inefficiencies during the post-apartheid period. The research aims at examining the effectiveness of the post-apartheid residential policies with emphasis on the ‘Breaking New Ground’ policy in meeting the government’s expectations of restructuring and transformation of spatial urban planning after 1994, between 2004 and 2011 in Walmer Township. More specifically, the objectives of the study were to determine the extent of eradication of informal settlements in the study area; functional integration to investigate the extent of transformation of the study area in terms of functional integration; and to analyse the financially sustainability of the area, focused on the road network. The study was theoretically and conceptually influenced by colonial and postcolonial policies that impacted on urban development and spatial planning in the former colonial city. Methodologically, both quantitative and qualitative approaches were adopted in this investigation and in a case study. The data used for the study was obtained from both primary and secondary sources. Primary data were collected by using a remote sensing technique and via face-to-face interviews, where the interviewees were selected at random from within the identified suburb areas. Secondary data were obtained from scholarly articles and books, and government agencies and departments. The Chi-square test of dependence was used and this was to determine whether there was a relationship between variables. The results indicate that there are over 3,000 informal settlement dwellings in 2011, and very little eradication of informal settlement has been achieved. Although there are signs of heightened efforts of functional integration, it still remains limited. It was revealed that the local government has missed opportunities to promote the BNG policy objectives, particularly in the application of higher density developments and to promote cost-effective road networks. Based on the outcomes of the study, there are clear signs of the post-apartheid governments’ slow pace to transform human settlements. The post-apartheid housing policies, in particular the BNG policy, have not effectively transformed human settlements as envisaged.
- Full Text:
- Date Issued: 2014
- Authors: Nagar, Manesh
- Date: 2014
- Subjects: Land settlement -- South Africa -- Port Elizabeth -- 21st century Human geography -- South Africa -- Port Elizabeth -- 21st century , City planning -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47992 , vital:40461
- Description: Spatial planning of human settlements in South African cities, particularly during the apartheid era, has been extensively investigated. Urban development in Nelson Mandela Bay (formerly known as Port Elizabeth) resembled most other South African cities and towns based on the informants of the apartheid spatial planning policies since 1948. Consequent to the colonial style urban forms, the typical South African city and town (including Nelson Mandela Bay) faces numerous challenges to eradicate the effects of the apartheid legacies of functional and structural inefficiencies during the post-apartheid period. The research aims at examining the effectiveness of the post-apartheid residential policies with emphasis on the ‘Breaking New Ground’ policy in meeting the government’s expectations of restructuring and transformation of spatial urban planning after 1994, between 2004 and 2011 in Walmer Township. More specifically, the objectives of the study were to determine the extent of eradication of informal settlements in the study area; functional integration to investigate the extent of transformation of the study area in terms of functional integration; and to analyse the financially sustainability of the area, focused on the road network. The study was theoretically and conceptually influenced by colonial and postcolonial policies that impacted on urban development and spatial planning in the former colonial city. Methodologically, both quantitative and qualitative approaches were adopted in this investigation and in a case study. The data used for the study was obtained from both primary and secondary sources. Primary data were collected by using a remote sensing technique and via face-to-face interviews, where the interviewees were selected at random from within the identified suburb areas. Secondary data were obtained from scholarly articles and books, and government agencies and departments. The Chi-square test of dependence was used and this was to determine whether there was a relationship between variables. The results indicate that there are over 3,000 informal settlement dwellings in 2011, and very little eradication of informal settlement has been achieved. Although there are signs of heightened efforts of functional integration, it still remains limited. It was revealed that the local government has missed opportunities to promote the BNG policy objectives, particularly in the application of higher density developments and to promote cost-effective road networks. Based on the outcomes of the study, there are clear signs of the post-apartheid governments’ slow pace to transform human settlements. The post-apartheid housing policies, in particular the BNG policy, have not effectively transformed human settlements as envisaged.
- Full Text:
- Date Issued: 2014